Prevalence of Coronary Heart Disease in India
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According to WHO (2007) coronary heart disease (CHD) (including Myocardial ischemia) is the most common cause of death in the world and the biggest cause of premature death in modern and industrialised countries (Lopez et al., 2006; Lindsay and Gaw, 2004). In 2001, ischemic heart disease accounted for 7.1 million deaths worldwide among which 5.7 million (80%) deaths were in developing and underdeveloped countries (Lopez et al., 2006). Although geographical variations such as ethnic origin and social class influence the CHD mortality rates (Lindsay and Gaw, 2004), coronary heart disease remains common globally despite the development of a range of treatments (Brister et al., 2007).
There is evidence that ethnicity is an important factor for coronary heart disease (Gupta et al., 2002; Brister et al., 2007) and a number of studies have suggested that there is increased incidence in coronary artery disease in South Asians (people originating from India, Pakistan, Bangladesh and Sri Lanka) when compared to the white population (Brister et al., 2007). South Asian people also have a greater risk of coronary heart disease than others from developed countries (Mohan et al., 2001; Joshi et al., 2007). In 2002 India had the highest number of deaths over 1.5 million due to coronary heart disease (Reddy et al., 2004). By 2010, it is expected that 66% of the world's heart disease is likely to occur in India (Ghaffar, 2004).
Therefore, this dissertation will focus on the prevalence of CHD in India and the impact of life style in the aetiology of CHD. There is wide range of evidence regarding the incidence and prevalence of coronary artery disease (CAD) in India (Reddy, 2004; Kasliwal et al., 2006; Patel et al., 2006; Brister et al., 2007), including Indian, British and Singaporean journal articles.
This dissertation is broken down into three parts: the first discusses the topic in relation to the existing literature on the prevalence of CHD in India; the second part is a critical appraisal of the risk factors and the impact of life style of CHD in Indians; While the third presents the management of CHD, and includes a discussion of the nursing implications and future research into this area.
THE DISEASE ASPECT- CORONARY HEART DISEAS/CORONARY ARTERY DISEASE
Coronary heart disease
“CHD covers a spectrum of disease such as angina, acute coronary syndrome, myocardial ischemia, ischemic cardiomyopathy, chronic heart failure and a proportion case of sudden cardiac death” (Lindsay and Gaw, 2004 pg no. 1).
Acute coronary syndrome
This is the clinical entity of myocardial ischemia and myocardial infarction.
“it is a condition that results from diminished oxygen supply coupled with inadequate removal of metabolites because of reduced perfusion to the heart muscle” (Woods et al., 2005 pg no. 541)
“A condition characterised by chest pain or discomfort from myocardial ischemia” (Woods et al., 2005 pg no. 541)
Overview of Coronary Artery Disease
CHD is the major cause of death in most countries and is considered almost to be an epidemic in western countries (Lippincott, 2003). In Britain it accounts for one in three deaths in men and one in four deaths in women, while 5,000,000 deaths annually are seen in US (Forfar and Gribbon, 2000). It is estimated that more than 80% of patients who develop clinically significant coronary artery disease (CAD), and more than 95% of those who experience a fatal CAD event have at least one major cardiac risk factor (Greenland and Klein, 2007). CHD is more prevalent in males, whites and the middle-aged, as well as elderly people. More than 50% of males age 60 or older show signs of coronary artery disease on autopsy. The peak incidence of clinical symptoms in females is between ages 60 and 70 (Lippincott, 2003).
There is a marked difference in death rates due to coronary disease between countries: for example, a 10-fold greater age-standardized death rate for men aged 35 to 74 years in Scotland compared with Japan. Within Europe, a threefold difference in death rates and disease incidence can be seen with Finland and the United Kingdom higher than Italy, France, and Spain (Forfar and Gribbon, 2000). There are also marked contrasts in coronary disease mortality trends between developed and developing countries. In the United States, Western Europe, and Australia, mortality has been falling between 15 and 50 per cent for at least 20 years (Lippincott, 2003). In contrast, rates continue to rise in Eastern Europe, including Poland, Hungary, Bulgaria, and the Czech Republic. The fall could be due to a fall in disease incidence or case fatality rates, or both. Although the management of acute myocardial infarction in particular has improved over this time, with case fatality rates halved, there has also been an increased awareness of risk factor avoidance (Forfar and Gribbon, 2000).
The Disease aspect
Coronary arteries bring blood and oxygen to nourish the heart. The heart pumps deoxygenated blood to the lungs, where it receives oxygen before it is pumped to the whole body. Because the heart is a muscle, it needs a continuous source of oxygenated blood to function.
Causes and symptoms
CHD is usually caused by atherosclerosis. Cholesterol and other fatty substances accumulate on the inner wall of the arteries, which in turn attracts fibrous tissue, blood components, and calcium to the inner walls of the arteries which then hardens into artery-clogging plaques (Woods et al., 2003). Atherosclerotic plaques often form blood clots that also can block the coronary arteries (coronary thrombosis). Congenital defects and muscle spasms can also block blood flow. Recent research indicates that infection from organisms such as the chlamydia bacteria may also be responsible for some cases of coronary artery disease (Warrel, 2003).
A number of major contributing factors increase the risk of developing coronary artery disease. Some of these can be changed and some cannot. People with more risk factors are more likely to develop coronary artery disease.
Major risk factors
Major risk factors are those factors that lead to CHD. They are mainly classified into two groups: non-modifiable and modifiable (Lippincott, 2003). Those that cannot be changed are the non-modifiable risk factors such as:
- Heredity - if a person's parents have coronary artery disease he/she is more likely to develop it.
- Sex - Men are more likely to have heart attacks than women and to have them at a younger age.
- Age - Men 45 years of age and older and women 55 years of age and older are more likely to have coronary artery disease. However now-a-days, coronary disease may occasionally strike a person in their 30s (Lippincott, 2003).
Major risk factors that can be changed (modifiable risk factors) are:
- Smoking - Smoking increases the chance of developing CHD and the chance of dying from it.
- High cholesterol - Dietary sources of cholesterol are meat, eggs, and other animal products. There are other factors also that increase the cholesterol level such as age, sex, heredity, and diet affect one's blood cholesterol. Total blood cholesterol is considered high when it is above 240 mg/dL and borderline at 200-239 mg/dL.
- High blood pressure - High blood pressure makes the heart work harder, also increases the risk of heart attack, stroke, kidney failure, and congestive heart failure. A blood pressure of 140 over 90 or above is considered high.
- Lack of physical activity - Lack of exercise increases the risk of coronary artery disease. Even modest physical activity, like walking, is beneficial if done regularly (Lippincott, 2003).
- Diabetes mellitus - the risk of developing coronary artery disease is seriously increased in diabetics. More than 80% of diabetics die of some type of heart or blood vessel disease.
Chest pain (angina) is the main symptom of coronary heart disease but it is not always present. Other symptoms include shortness of breath, and chest heaviness, tightness, pain, a burning sensation, squeezing, or pressure either behind the breastbone or in the arms, neck, or jaws (Lindsay and Gaw, 2004). Many people have no symptoms of coronary artery disease before having a heart attack: according to the American Heart Association 63% of women and 48% of men who died suddenly of coronary artery disease had no previous symptoms of the disease (Woods et al., 2001).
THE COUNTRY PROFILE - INDIA
The country India
India, situated in the South Asian region, is the seventh largest, and the second most populous, country in the world with a population of 1.103 billion (United Nations Population Division, 2005) in 32 states and union territories covering about four thousand towns and cities and about six lakhs villages (Nag and Sengupta, 1992). The population distribution is 71% rural and 29% urban (United Nation Population Division, 2005).
Initially, India was a rural economy that subsequently participated in the industrial revolution with the help of colonial rule. After independence in 1947, the country followed socialist policies and hence large-scale infrastructure and industry development was carried out through the public sector. By the early 1990s, the Indian economy was opened up through liberalization and is now on the road to privatization through disinvestment policies. However, the economic growth in India during the 1990s as a result of the 1991 economic reforms has also seen an increase in poverty and a radical transformation in the well-being of the bottom half of the population (Rajeshwari et al., 2005). The consequences of these economic and social changes have led to an epidemiological transition (Joshi et al., 2006). An epidemiological transition is a focus on the complex changes in the patterns between the health and disease and the interaction between them and various other factors such as demographic, economic and determinants with their consequences (Omran, 2005).
The urban population has increased by 4.5 times during 1951-2001 (WHO, 2000). The life expectancy from birth for males is 62 and females 64 (WHO, 2008). While the crude mortality rate is decreasing the percentage of children under 15 is declining (WHO, 2007).
Total expenditure on health per capita (Intl $, 2006): 109. Total expenditure on health as % of GDP (2006): 4.9 (WHO, 2008). The leading cause of mortality after death during childbirth is cardiovascular disease, accounting for 188 deaths per 100,000 population (WHO, 2005).
The health care system of India is overseen by two different bodies:
- The Department of Health & Family Welfare.
- The Department of AYUSH (Ayurvedic, Unani, Siddha and Homeopathic Medicines).
Each state has a Ministry of Health & Family Welfare although their organization differs from state to state. Generally, there is a Directorate of Health Services providing technical assistance. Some states have a separate Directorate of Medical Education & Research, and some have a separate Director of Ayurveda or Director of Homeopathy (WHO, 2007). In rural areas, Community Health Centres serve estimated populations of 100,000 and provide speciality services in general medicine, paediatrics, surgery and obstetrics & gynaecology. However, there is still a shortfall in the number of community health centres in the rural areas of India. A Primary Health Centre (PHC) covers around 30,000 people (20,000 in hilly, desert or difficult terrain) and is staffed by a medical officer, and one male and one female health assistant along with supporting staff. A sub-centre serves around 5,000 people (3000 in difficult terrain) and is supported by one male and one female multipurpose health worker. These workers and health assistants have different designations in different states.
Playing an equally important role in curative and preventive care in urban areas is the private sector. A large number of private practitioners exist and there are many large and small hospitals and nursing homes along with a large number of voluntary organizations providing health care (Bhat, 1993).
Chapter One: Literature Review
The aim of this review is
- To analyze the prevalence of CHD in India
- To analyze the mortality rates related to CHD
- To understand the aetiology of CHD in India
This review will also include a comparison study of the prevalence of coronary heart disease among migrant Indians and the natives of the particular migrant destination countries.
Reason for the selection of the topic
CHD remains the largest cause of death worldwide. Mortality rates from cardiovascular disease have been known to increase from five-fold to ten-fold around the world (National Institute of Health, National Heart, Lung and Blood Institute, 2000). A World Health Organisation (WHO) Multinational monitoring of trends and determinants in cardiovascular disease (MONICA) study analysed the event rates of CHD among 38 populations between the age group 35-64years, and found variations in CHD prevalence and mortality rates among different ethnic groups (Tunstall-Pedoe et al., 1994).
India is a developing country which is seeing an increased rise and prevalence of CHD (Reddy, 2004). While the incidence of coronary artery disease (CAD) has decreased by 50% over the past 30 years in developed countries, in India it has doubled (Kasliwal et al., 2006). Prevalence is an epidemiological measure to determine a how commonly disease or condition occurs in a population, whereas incidence is another epidemiological measure that measures the rate of occurrences of new case of a disease or condition (Le and Boen, 1995). The prevalence of CHD is seen mostly from the age of 35 years and over (Kasliwal et al., 2006).
CHD is the second leading cause of mortality in Indians (Patel et al., 2006). Joshi et al., (2006) conducted a survey in the rural areas of Andhra Pradesh, India, the results of which suggested that vascular diseases (including ischemic heart disease and stroke which accounts for 32%) are the main cause of mortality in India when compared to other chronic conditions such as infectious and parasitic diseases, tuberculosis, intestinal conditions, HIV, neoplasm and diseases of the respiratory system.
However, CHD mortality rates have decreased in by 50% in most industrialised countries since 1970s (Unal et al., 2004). In United States the decline was seen during the 1980s (US Department of Health and Human Services, 2000), while in the United Kingdom the decline saw a slower pace (British Heart Foundation, 2003). In the United Kingdom the death rates fell by half in the 55-64 age group and slightly less than 40% in men aged 35-44. In women death rates fell by half and a third in those aged 55-64 years and 35-44 respectively (British Heart Foundation- BHF, 2004). However, even though the mortality rates from CHD have fallen it does not suggest that the prevalence has also fallen. The reasons for the decline are not clearly understood but some hypothesise that a reduction in smoking; management for lipid and blood pressure control; modern care for acute coronary syndrome; and secondary prevention has contributed (Luepker, 2008).
The increased incidence of CHD has led to the increase in number of Coronary Artery Bypass Grafts (CABG) and other cardiac surgeries. It is estimated that 25,000 CABG surgeries are carried every year in India (World Health Organisation Statistical Information System, 2003). Hence, it could be noted that in a highly populous country like India with its increased prevalence of CHD that the estimated CABG surgeries reaching to the public is actually very few. Therefore, there could be considerable gap between the public need and treatment.
Therefore, the reason for this thesis is to help us understand that there is high prevalence in CHD in the Indian population; the specific reasons for this increased epidemic; and how can it be managed so the population can remain healthy.
The literature was searched with the specific intention of examining the most up-to-date data concerning the prevalence of CAD in India. The search was performed by accessing specialised scientific medical and nursing databases carrying articles regarding the specified subject area (Craig and Smyth, 2002). The databases accessed included the Cumulative Index of Nursing and Allied Healthcare Literature (CINAHL), Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, and MEDLINE and EMBASE using the Ovid SP interface. The keywords used for the search were: coronary artery disease, ischemic heart disease, and coronary heart disease, South Asians, prevalence, mortality rate, British white, Caucasians and India. The Boolean term AND was used simultaneously.
The date range of the studies targeted was set between 1991 and 2009; and was chosen so the most recent evidence could be drawn on, although articles outside this date limit were also incorporated into the search so as to be able to compare whether there have been any changes in the literature over time. To focus the search more strategically the following inclusion and exclusion criteria below were applied.
Inclusion and exclusion criteria used to narrow the search
The inclusion criteria include prevalence of CHD in both rural and urban areas in order to compare the prevalence of CHD, the date range was set from 1991-2009 so that the recent evidence could be drawn on. The other inclusion criterions were British Indians, American Indians, migrant Indians and South Asians. The patient age group considered was from 35 years over as this matches the known incidences of coronary artery diseases (Kasliwal et al., 2006). The exclusion criteria were other cardiovascular studies such as peripheral artery disease since the literature review focussed on CAD only.
Initially the search revealed 78 potentially relevant papers; however 48 did not contain data pertinent to the inclusion criteria or were not credible sources. The 30 papers that were used for the review included both qualitative and quantitative studies. They included a wide range of international literature to allow a comparison of the prevalence of CHD between British Indians and British whites. The literature that provided evidence from the Indian health care system were all medical journal articles by authors such as Bhardwaj, 2009; Mandal et al., 2008; Kamili et al., 2007; Chow et al., 2006; Patel et al., 2006; Kuppaswamy and Gupta, 2005; Patel et al., 2005; Sharma and Ganguly, 2005; Ward et al., 2005; Indrayan, 2004; Pinto et al., 2004; Gupta et al., 2003; Gupta and Rastogi, 2003; Gupta et al., 2002; Singh et al., 1997; Gupta et al.'s 1997; Dhawan, et al 1996; Gupta et al., 1995; Gupta et al., 1993; Kutty et al. 1992. Journals from UK include Zaman et al., 2008; Whincup et al., 2002; Bhopal et al., 1999; Cappuccio et al., 1997; and Journal from Singapore are Mak et al., 2004; Tai and Tan, 2004; Kam et al 2002; Lee et al., 2001.
From the analysis of the above literature the following themes were formulated
- The prevalence of CHD in the mother country, India, both in rural and urban areas.
- The reasons for the increase in CHD in India.
- A comparison of CHD prevalence and mortality rate between British Indians and British whites.
Credibility of the Literature
In order establish the evidence of increased prevalence of CHD in India it is necessary to analyse a wide range of literature. To assess the credibility and reliability of the evidence, the strengths and limitations of the texts were identified. Systematic reviews were used to determine the strength of the evidence. In the hierarchy of evidence, systemic reviews are considered the 'golden standard'. This is because systemic reviews draw on
“Statistical procedure[s] for combining data from a number of studies and investigations in order to analyse the therapeutic effectiveness of specific treatment or interventions....”
(Helewa & Walker, 2000, p.111).
There was only one systematic review available for this literature review (Bhopal et al., 2000). This research paper has a clear search strategy stated, limits, and selection criteria. The search was limited to English research papers, however one exception was that only published studies reporting original comparative data were included. Unpublished studies and studies only reported as abstracts were not included, which ensures rigour in the analysis of the data by having a complete recount of the different studies; this also ensures that the studies had gone through an evaluation committee before being published. The conclusions reached in the systematic reviews support the conclusions reached across the other literature sourced (Mandal et al., 2008; Gupta et al.,1997).
Observational studies are considered a good source of evidence, and are similar to Randomized Controlled Trials (RCT's) in terms of effectiveness, appropriateness, and feasibility of the evidence (Craig & Smith, 2002). The studies examined as part of this essay also described the setting, location, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection, thereby increasing their robustness (STROBE checklist, 2008). There was one observational study that mentioned its location, time period and setting, and therefore provided credible evidence for the literature review (Wilkinson, 1996).
Most of the studies analysed for the literature review were population based surveys, while some studies were clearly addressed and statistically analysed (Mandal et al., 2008; Zaman et al., 2008; Chow et al., 2006; Patel et al., 2005; Mak et al., 2003; Whincup et al., 2002; Lee et al., 2001; Bhopal et al., 1999; Cappuccio et al., 1997, Gupta et al., 1997; Singh et al., 1997; Kutty et al., 1992) ethical issues were mentioned (Cappuccio et al., 1997; Kutty et al., 1992). Some studies however did not explain their statistical analysis (Bhardwaj, 2009; Pinto et al., 2004), and without knowing the specific characteristics of the statistical analysis, the studies cannot be replicated as evidence in this literature review.
In regard to qualitative research, a great deal of debate is still going on regarding how to assess the quality of such work (Sandelowski, 1986). In particular, researchers suggest that it is difficult to develop a single benchmark against which the true value of claims can be judged (Craig & Smith, 2002). Even though qualitative studies are not considered excellent or even good sources of evidence, based on evidence-based hierarchy, they can address questions that cannot be answered using other experimental methods (Green & Britten, 1998). One qualitative study in the literature was used to examine and compare the illness beliefs of South Asian and European patients with coronary heart disease (CHD) about causal attributions and lifestyle change. The method of sampling and data analysis was appropriate.
Although the reviews of the literature accessed for this literature review did not prove as rigorous as other sources of evidence, because they did not draw on empirical data, they were used to support the findings of other more robust forms of evidence, which were generated from systematic reviews, observational studies and survey. Reviews of the literature carried out by Goyal and Yusuf, 2006; Kuppaswamy and Gupta, 2005; Sharma and Ganguly, 2005; Tai and Tan, 2004; Barakat et al., 2003; Yusuf et al., 2001; Reddy et al., 1998 provided evidence, however the paper fails to present a search analysis.
Evaluation of key studies
The prevalence of CHD in India
Coronary heart disease has emerged as an epidemic in India (Gupta and Rastogi, 2003). According to the National Commission and Macroeconomics and Health, Government of India the total number of CHD patients in India by the end of the century was around 30 million (5.3% ) of the adult population; this is forecast to increase to up to 60 million cases (7.6%) by the year 2015 (Indrayan, 2004). Although there are various comparative studies showing the burden of cardiovascular disease among Indian immigrants in Western countries, there has been less attention paid to CHD in India itself (Goyal and Yusuf, 2006, Reddy et al., 2004, Yusuf et al., 2001, Anand et al., 2000). Hence, this section of the literature review will focus on the prevalence of CHD in India.
In developed countries, there are no rural-urban differences in the prevalence of CHD (Feinleib, 1995). However in India there is marked difference between the prevalence of CHD in the rural and urban areas with surveys showing that the prevalence rate of CHD in urban areas is about double that rural areas (Gupta et al., 2006; Reddy, 1998; Singh et al., 1996; Singh et al., 1997).
Studies have been done in various states of India of the prevalence of CHD in the country. For example, Mandal et al., (2008) conducted a cross-sectional survey among the urban population of Siliguri in West Bengal, from a random sample population aged greater than or equal 40 years, to determine the prevalence of ischemic heart disease and the associated risk factors. The results showed that 11.6% had ischemic heart disease (IHD) and 47.2% had hypertension. Males had a higher (13.5%) prevalence of IHD than females (9.4%). About 5% of the patients had asymptomatic IHD. However, this study had a small sample size, which could limit the generalisability of the findings and is limited by the fact that other risk factors like diabetes and lipids were not included.
On the other hand, Kutty et al. (1992) conducted a survey among the rural population of Thiruvananthapuram district in Kerala state, to analyse the prevalence of some indicators of coronary heart disease. The indicators included in the study were ECG changes and well-known risk factors such as obesity, hypertension, smoking and diabetes. From the above criteria it was found that rural Thiruvananthapuram has a lower prevalence of coronary heart disease when compared to urban centres like Delhi. However there were drawbacks to this study too, such as the fact that people were sampled on the basis of household list from the panchayat office (panchayat is south Asian rural political system) so anyone who did not belong to the house list in the panchayat was not included in the study. This could have caused a limitation in the generalisability of the results as there was bias in sampling technique.
Similarly, Singh et al., (1997) conducted a cross- sectional survey in two villages in Northern India, which showed a significantly higher and increased prevalence of CHD in urban areas compared to rural areas. Reddy also (1998) conducted a cross-sectional survey which found the prevalence rate of CHD as being 6% in the rural areas of Haryana, India. Another study conducted was in the rural areas of Northern India in Himachal Pradesh which showed a CHD rate of 4.06% among the whole rural population in the age group between 50-59 years with a slightly higher incidence in men than women (Bhardwaj, 2009). However these research papers failed to set out their statistical analysis or research analysis, meaning that the reliability of the papers cannot be measured. Nonetheless, it can be noted that the prevalence of CHD was lower in the rural areas and also that the prevalence rates varied in different states of India.
Chow et al., (2006) conducted a survey in the rural areas of Andhra Pradesh to investigate the prevalence of cardiovascular disease and levels of managing the major risk factors. Their results showed that cardiovascular disease is highly prevalent and the community knowledge about cardiovascular disease is quite good. However, the results also pointed out that even though people have the knowledge, their management for risk factors remains suboptimal. Hence it could be suggested that even though the people had good awareness regarding CHD the care provided for them was insufficient.
Additionally there were a number of studies done to determine the increase in CHD prevalence in urban areas compared to rural areas of India (Pinto et al., 2004; Gupta et al., 2002; Gupta et al., 1995). However there are limitations to these studies, including such factors as: small and variable samples, low response rates, inappropriate diagnostic criteria, non-specific electrocardiographic changes, a lack of standardization, or incomplete results.
Gupta et al.'s (1997) survey in a rural area (Rajasthan) found that even though the prevalence of CHD was lower in the rural areas, it had nevertheless increased (to 3.4% in males and 3.7% in females) when compared to previous studies. The study was carried out with a detailed questionnaire prepared according to guidelines from the World Health Organization (WHO) the United States Public Health Service and a based on a review of previous Indian studies. The Performa elicited: family history of hypertension and CHD; social factors such as education, housing, type of job, stressful life events, depression, participation in religious prayer and yoga; along with conventional risk factors such as smoking, alcohol intake, amount of physical activity, diabetes, and hypertension. Blood pressure measurements and a 12 lead ECG using proper standardization were performed on all participants. Earlier studies from India used different criteria and showed higher CHD prevalence. When the diagnostic criteria in the present study are extended to include past documentation, response to WHO-Rose Questionnaire and ST-T wave changes in ECG as done in previous studies, the prevalence rises to a rate higher than those found in previous Indian rural studies. However, the results cannot be validated. For example, some of the previous studies from India included ECG criteria as the presence of left bundle branch block, complete heart block and presence of ST segment and T wave changes while some studies suggest that these findings are not reliable enough to diagnose CHD, especially so in females where ST-T changes may be non-specific (Reddy et al., 1996; Gupta et al., 1993). That said, it is clear evidence that there is still an increasing prevalence of CHD in India.
Heart diseases are also occurring in Indians 5 to 10 years earlier than in other populations around the world (Dhawan, et al 1996). According to the INTERHEART study, the median age for first presentation of acute Myocardial Infarction (MI) in the South Asian (Bangladesh, India, Nepal, Pakistan, Sri Lanka) population is 53 years, whereas that in Western Europe, China and Hong Kong is 63 years, with more men than women affected (Yusuf et al 2004) (the INTERHEART study was a standardized case-control study that screened all patients admitted to the coronary care unit or equivalent cardiology ward for a first MI at 262 participating centres in 52 countries throughout the world).
Epidemiological studies have shown that immigrant Indians share a significantly higher incidence of CHD than the native populations (Enas et al., 2005; Gupta et al., 2002). The first evidence of this was found in a 1959 study among expatriate Indians in Singapore (Kuppaswamy and Gupta, 2005). Similarly many studies have been done in various other countries to corroborate these findings (McKeigue, 1991; Enas et al., 2005). However, in the UK it is only recently that the importance of ethnicity and disparities in regard to CHD has been realised (British Heart Foundation, 2004). Several studies have reported that there is increased prevalence of CHD in British Indians when compared to British Whites (McKeigue, 1991; Bhopal et al., 1999; Enas et al., 2005).
Hence, the review of the literature clearly shows the prevalence of CHD among the urban and rural populations in India, and provides strong evidence that the prevalence of CHD is higher in urban areas and among Indian males.
Another factor for concern is the prevalence of CHD based on socio-economic group. A systematic review by Gonzalez et al., (1998) suggested that prevalence of CHD and socio-economic group are inter-related. Singh et al's., (1997) cross-sectional survey had 1767 subjects (894 males and 875 females; 25-64 years of age) who were randomly selected from two villages of India. They were divided into social classes 1 to 4, according to education, occupation, housing conditions, ownership of land, ownership of consumer durables and per capita income (social classes 1 and 2 were mainly high and middle socio-economic groups and 3 and 4 low income groups). The prevalence of CAD was significantly higher among classes 1 and 2 in both sexes. While in developed countries the increase in CHD was due to poor education and unemployment, in India dietary intake is related to socioeconomic status: forty-five percent of the available fat is consumed by the higher income groups (Expert Group of the Indian Council of Medical Research, 1990).
Therefore from the above article it is can be noted that socio-economic status plays a vital role in the prevalence of CHD. People from rural India often have few resources, are unemployed and poorly uneducated, and hence are untreated. However, the incidence of CHD is higher in higher income groups due to dietary factors.
Of particular concern to the Indian government is not only the heavy burden of cardiovascular diseases, but also the effects of cardiovascular disease on the population, especially the productive workforce aged 35–65 years (Sharma and Ganguly, 2005). According to a WHO report in 1990, the proportion of CVD deaths occurring below the age of 70 years was only 26.5% in the developed countries but was 52.2% in India. A survey showed that CHD is the main cause of mortality (attributable to ischemic heart disease and stroke) when compared to other chronic conditions such as infectious and parasitic diseases, tuberculosis, intestinal conditions, HIV, neoplasm and diseases of the respiratory system (Joshi et al., 2003).
In the UK the South Asian CHD mortality rate is 1.5 times higher than that of the white population (Wild and McKeigue, 1997).
- (Source: Wild and McKeigue, (1997) Ethnic differences in Cardiovascular disease)
A mortality study (Balrajan, 2000) carried out in England and Wales showed that mortality from IHD was highest in people from the Indian subcontinent (standardized mortality ratio 136 and 146, respectively) with young Indian men experiencing the greatest excess mortality (313 at ages 20–29).
It is evident therefore, that CHD is the one of the leading causes of mortality among Indians and other South Asians. The review of the literature also provides an insight into the rapid progression of an epidemiological transition in India.
It must be emphasized that although there is a higher prevalence of CHD in males than females, the median age of presentation is higher in women and they are known worldwide to have a poorer prognosis compared with men (Mak et al., 2004). Younger Asian women have a worse survival rate, of only 28 days after acute MI (Kam et al 2002). The reasons for higher mortality in younger women are still not fully understood but may be related to the presence of different risk factors in women, co-morbidities, severity of infarction, and response to treatment. Hence while men have a higher incidence of CHD, women have a poorer prognosis from CHD.
In India the main reasons for the increasing rate of CHD are a rising population and the high prevalence of CHD risk factors, with one of the main risk factors being urbanization (Goyal and Yusuf, 2006). Urbanization can characterized by intake of energy dense foods, decreased physical activity, and increased psychological stress which ultimately leads to hypertension and dyslipidemia (Yusuf et al., 2001). In western countries during the 20th century the growth of urbanization brought about an increase in the rate of CHD (Gupta et al., 2003). This epidemiological trend went hand in hand with changes in lifestyle, specially an increase in the consumption of processed, energy-dense food, fast food outlets such as KFC, McDonalds (and especially roadside food stalls in India) and a dependence on machines for physical work (Yusuf et al., 2001).
The evidence also shows that some ethnic groups may be at particular risk when exposed to an urban environment and also suggests that genetic factors may also be involved. This situation is especially relevant to the experience of Chinese, Malays and Indians residing in Singapore, where Indians have a three times higher rate of myocardial infarction when compared to the Chinese - despite their exposure to a similar environment (Lee et al., 2001). However, genetic factors alone do not seem to explain the differences in the prevalence of CHD between ethnic groups either. Rather, it could be identified as a complex interplay of both environment and genetic factors that give rise to these ethnic differences (Tai and Tan, 2004). Additionally, some genetic variants appear to identify subgroups of the population that are maladapted to an urban lifestyle. For example, a high fat diet is associated with higher serum triglyceride and lower HDL-cholesterol concentrations. Therefore, it is evident that urbanization, an increased fat diet and changes in lifestyle can lead to CHD. This might be the reason as well as the answer for Indian immigrants who have to change their life style according to their respective migrant destination countries.
However there is an established high rate in CHD in Indians residing in the UK. The reason is still unknown, although some studies suggest that it seems likely to be influenced by genetic factors (Whincup et al., 2002). Evidence also suggests that South Asians (from India, Pakistan, Sri Lanka, Burma and Bangladesh) have poor outcomes from CHD (Wilkinson et al., 1996; Mather et al., 1998).
Kumar et al., (2000) conducted a cross-sectional survey which showed that urban residents had an increased prevalence of CHD due to increased cigarette smoking, increased alcohol consumption and increased fatty food intake. These factors were found to be the crucial troublemakers that lead to CHD.
This review demonstrates that urbanization is the reason for the increasing prevalence of CHD in India. It is also evident that urbanization leads to increased cigarette smoking, increased alcohol consumption and increased fatty food intake. This analysis also showed that even migrant Indians showed an increase in the prevalence of CHD when compared to British whites (40%) due to their pronounced differences in diet and lifestyle (Singh et al., 2001; Singh et al., 2000). Therefore the second part of the dissertation will critically appraise the risk factors that cause CHD.
From the above literature review the following points were noted
- CHD is an emerging epidemic among the Indian population.
- It affects men early age.
- CHD is prevalent in both urban and rural areas of India, but is more prevalent in urban areas.
- There is slight increasing trend in the prevalence of the disease in both urban and rural areas.
- Immigrant Indians share a significantly higher incidence of CHD than the destination countries' native populations.
- Women who experience CHD at a later stage in life have a poorer prognosis when compared to males.
- The increase in CHD is due to urbanization and changes in life style.
- Obesity, hypertension, smoking and diabetes are considered as risk factors for CHD in rural areas.
The risk factors that leads to CHD in India
Because Indians represent almost a quarter of the world's population, and India has an increased prevalence of CHD, it is therefore important to determine the risk factors unique to India so as to identify of tailored strategies for the prevention of cardiovascular disease. However, the aetiology and mechanism leading to the development of CHD at higher rates among Indians (both in India itself and among migrants elsewhere) remain incompletely understood (Ghosh et al., 2003). CHD risk factors show s graded increase in urban areas, higher social classes, and among Indian immigrants, which are related to pronounced differences in diet and lifestyle (Singh et al., 2001; Singh et al., 2000). Since the main aetiology for coronary heart disease is atherosclerosis, is necessary to identify the reasons for its apparently increased incidence in Indians, especially since atherosclerosis and conventional risk factors are considered as the principal contributors to the pathogenesis (Ross, 1999).
Lifestyle and risk of CVD in Asian Indians
The review of the literature in Chapter One showed that occurrence of CHD was related to changes in life style; therefore, this section will critically analyze in detail the risk factors of CHD.
Physical inactivity is responsible for at least a two-fold increase in risk for CHD events and CHD mortality (Rajeshwari et al., 2008). Physical inactivity also tends to play a role in causation of other CHD risk factors such as hypertension, diabetes mellitus, obesity, and hypercholesterolemia (Tanasescu, 2002). Enas (2002) suggested that decreased physical activity and increased consumption of calories and saturated fat contribute to abdominal obesity, insulin resistance and atherogenic dyslipidemia. Rastogi et al., (2004) carried out a case control study in two hospitals in urban areas in Delhi and Bangalore, India, which showed that there was an increased incidence of CHD among those individuals living a sedentary lifestyle, particularly among those who viewed a lot of television. It was also found that there is a strong inverse association between leisure-time exercise and CHD. The potential limitation of that study is that there may be a selection bias as the researcher included only patients who survived.
Tobacco smoking is considered one of the major risk factors leading to increased CHD, it is also considered to interact with other risk factors such as diabetes mellitus, hypertension and low high density lipoprotein (HDL) and to increase the risk of CHD (Bhatt, 1992). The World Development Report (1993), an annual report that examines the interplay between human health, health policy, and economic development, suggested that that tobacco smoking would lead to increased pulmonary disease and CHD in India by the year 2000. In India, males smoke cigarettes or another type of small unfiltered cigarettes hand rolled in temburni leaves, which are known as bidis (Gupta, 2000). Research (a case-control study) has shown that the risk of CHD among smokers is five times greater than for non-smokers (Bagchi et al., 2000). However, the results cannot be generalised as the sample size was small.
A case-control study by Rastogi et al., (2005) suggested that smoking bidis carries a high risk of MI, although the study did not show that bidis carry a higher risk of MI when compared to other conventional tobacco products. This research paper also did not show the statistical analysis of the research work. Intake of alcohol combined with smoking, which is prevalent in India, was found to increase the risk of cardiovascular disease (Friedman, 1992); however no significant statistical association was found between alcohol consumption and CHD in the study by Bagchi et al (2001).
Diet is considered to be one of the earlier risk factors, as when one's diet changes in terms of quantity or quality it can increase the occurrence of main CHD risk factors like obesity, diabetes, hyperlipidemia and hypertension (Bedi et al., 2006; Rajeshwari et al., 2008). A large proportion of the population of India adheres to a vegetarian diet due to cultural and religious reasons. A typical Indian diet is based on cereals; in a low fat lactovegetarian diet where most fat consumed is unsaturated fats from cooking oils (Rajeshwari et al., 2005). Not only the fat and cholesterol in dairy products, but also the animal protein and milk carbohydrates are linked to heart disease (Lofti et al 2008). A large survey covering 19 western countries concluded that heart disease mortality rises as consumption of milk protein rises (Tanasescu. 1994).
Singh et al., (1996) conducted a cross-sectional survey in Moradabad, India; they reported that subjects who consume trans fatty acids (vegetable ghee) plus clarified butter (Indian ghee and a milk product) or those consuming clarified butter as a whole had a significantly higher prevalence of coronary artery disease compared to those consuming clarified butter plus vegetable oils (Singh et al., 1998). Ghee (clarified butter) consumption leads to increased levels of transfatty acids and lower levels of linoleic and linolenic acids in adipose tissue, both of which are considered to increase the risk of CHD (Chaturvedi, 2003). In some parts of India, trans fats from hydrogenated vegetable oil in the form of vanaspati are consumed in greater quantity (Singh, 1996). It is logical that dairy products and fat products need to be examined, as cooking methods form a major source of fat in Indian diets when compared to the past. It is a common message for the public that certain cooking methods are harmful as they increase the risk factors for CHD. This could be explained by the fact that this method of cooking medium can lead to hypercholesterolemia or dyslipidemia.
Hence the research concluded that although the conventional risk factors such as physical inactivity, smoking and dietary patterns explain the higher rates of cardiovascular disease among Indians, they nevertheless do not explain their increased rates of CHD when compared to other ethnic groups. The increased risk of cardiovascular events could be due to factors affecting plaque rupture, the interaction between prothrombotic factors and atherosclerosis, or as yet undiscovered risk factors. Ethnicity-based research can identify new clues to the pathogenesis of a disease, since the populations under study are heterogeneous in lifestyle and genetic characteristics (Anand et al., 2000).
Other risk factors
Conventional coronary risk factors, including smoking, hypercholesterolemia, and hypertension, do not explain Indians' increased CHD risk compared with whites (Chambers et al., 2009). Although diabetes and insulin resistance are more prevalent among Indians, the precise mechanisms underlying the increased CHD mortality in Indian are not known. Yusuf et al (2004), and the INTERHEART study established an association between conventional modifiable risk factors for MI in all regions of the world, including South Asia, and in both sexes and at all ages. In South Asians, apolipoprotein and smoking were the important risk factors, as in the rest of the world. However, hypertension, abdominal obesity, and diabetes had more severe effects in South Asia.
Therefore, we will critically analyse in detail those risk factors that lead to CHD in India that are unique when compared to another ethnic group such as British whites. There are many risk factors that lead to CHD however; this piece of work will look in detail the following:
- Increased cholesterol levels
- Total plasma homocysteine
- C-Reactive Protein
Increased cholesterol levels
An epidemiological study in an Indian population has revealed that there is a dependable and strong relationship between plasma total cholesterol (TC) and the incidence of CHD (Kannel, 1995). Total cholesterol levels is regarded as a primary factor in CHD rates in Indian populations (Roberts, 1995) and are significantly higher when compared to other Asians (such as Pakistanis, Bangladeshis and Sri Lankans) (Enas, 1997).
The Jaipur Heart Watch-2 study is a prospective study from North India that found a high prevalence of classical risk factors for CHD in urban residents: namely hypercholesterolemia among all the other conventional risk factors, in residents of the city of Jaipur (Gupta et al., 2002). This study reported that one of the risk factors leading to CHD and the most common dyslipidemia was low HDL in both genders; however the total cholesterol levels were eight times higher in men (37.4%) than women (4.1%), while the low density lipoprotein level (LDL) was higher in women (45.8%) than men (37%). This study had an ample sample and the results are generalisable to the urban population.
Hyperlipidemia was another risk factor that seemed to be highly prevalent in young Indians with CHD (Pinto et al 1992; Gupta et al 2002; Goel et al 2003). However, in a comparison between north and south India differences appear to exist between the lipid levels with patients and individuals without CHD. The analysis revealed that the north Indians manifest the disease when cholesterol levels are low (Goel et al 2003). In addition, a greater role can be attributed to total cholesterol and LDL-C in atherogenesis in the younger Indian population with angiographically proven CAD. The low level of HDL cholesterol and increased triglyceride level is widespread in the Indian population in both younger and older people (Mohan et al 2001; Goel et al 2003). Even in the INTERHEART study (Yusuf et al 2004), the highest population attributable risk factor (PAR) was abnormal lipids in both sexes. These studies indicate that abnormalities in lipid metabolism play an important role in the development of CHD in young Indians. The limitation for this study is that the risk factors were ascertained or measured on the basis of patient history which has the potential to create some errors in the study,
While the above studies show increased cholesterol levels are a risk factor of CHD among Indians in India; Patel et al., (2006) conducted a survey to compare CHD among Gujaratis in Britain and their counterparts in the villages of origin in India. This study shows that the one of the main cause of increased prevalence of CHD among the migrant Gujaratis is due to the established increased cholesterol level which is as a result of nutrition and a lack of physical activity. However, the rural areas of India tended to show a lower prevalence rate of CHD than among the British Gujaratis, those from the urban areas of Gujarat in India had similar results to those of the migrants. This was due to the previously mentioned factor of urbanization.
Low levels of TC and HDL-C were observed in patients when compared to controls (Rajeshekar et al., 2004). Low levels of HDL-C are reported to increase the risk of CHD even when total cholesterol is not elevated (Gambhir, 2000). The potential limitation of the study is that in India, sampling frames were constructed from the 1999 electoral roll allocation to each household hence any who were not on the roll were not sampled in that particular area.
Therefore, serum cholesterol is directly related to the increased prevalence of CHD among the Indian population. This is due to changes in life-style.
Another susceptible risk factor is hyperglyceridemia. In migrant Indians, serum triglyceride levels have been consistently found to be associated with CHD (McKeigue, 1989 as cited in Mohan and Deepa, 2004). However in native Indians, LDL cholesterol and total cholesterol/HDL cholesterol (Mohan and Deepa, 2004) are of greater significance. The Paris Prospective Study and Edinburgh-Stockholm Study have implicated hypertriglyceride in the etiology of CHD, while many other studies have also shown that increased triglycerides is a risk factor for CHD (Mohan et al., 2000; Rajeshekar et al., 2004; Patel et al., 2006). Research from the UK and the United States revealed higher plasma triacylglycerol levels among emigrant Indians than those of European origin (Miller 1988 as cited in Rajeswari et al., 2005). In India a Chennai Urban Population Study (CUPS) survey showed that LDL and age were risk factors for CHD but serum triglyceride levels did not come out as an independent variable (Mohan et al., 2001). One of the potential biases of that study is that being a cross-sectional one, it represents only survivors of MI.
Similarly Rajmohan et al.'s (2000) analysis showed age, male sex, hypercholesterolemia and high low-density lipoprotein levels to be strongly associated with coronary artery disease. Among South Indian type 2 diabetic subjects, serum isolated hypercholesterolemia and high low-density lipoprotein cholesterol - but not isolated hypertriglyceridemia (HTG) - appear to be associated with CAD. A recent report based on analyses of data from the Multiple Risk Factor Intervention trial and three other trials concluded that triglyceride measurements do not provide clinically meaningful information about coronary heart disease risk beyond that obtained by cholesterol measurements (Avins et al., 2000). The potential limitation for the study was that only a single baseline measurement of triglyceride was used. Triglyceride measurements are less precise than other lipid measurements and this variability may cause the assessment of triglyceride-CHD associations to be underestimated. However, Mehta et al (1987; cited in Rajeshwari et al., 2005) suggested an association between HTG and high plasma levels of the tissue plasminogen activator inhibitor, which may thereby be an important factor underlying the pathogenesis of CHD.
Lipoprotein is termed ‘the deadly cholesterol'. It is a variant of LDL particle which has in addition to apolipoprotein B, apolipoprotein(a) (Lp(a)). Among the two, Lp(a) is a strong independent risk factor for premature CAD in many populations including Whites (Uterman et al., 1995; Lippincott et al., 2003). Apo Lp(a), which is a constituent protein of Lp(a), has considerable homology with fibrinogen and not only interferes with fibrinolysis, but also is retained in the arterial wall, thus contributing to atherogenesis (Bedi et al., 2006).
Enas et al., (1994) were the first to report high plasma levels of Lp(a) in Asian Indians. A genetic predisposition to CHD in Indians is strongly supported by several reports of high levels of Lp(a) in Indian populations in the UK (Shaukat, 1994). A cohort study by Bhatnagar et al., (1995) compared coronary risk factors in migrants from India of Punjabi origin with their siblings who had stayed back in India. They found that both groups had a higher level of serum lipoprotein(a) (levels that are largely genetically determined and not affected by diet) as compared with Europeans.
Similarly, a case- control study by Rajeshekar et al., (2004) reported increased lipoprotein in patients with CHD, higher Lp(a) levels in females when compared to males in patients; and higher Lp(a) levels in individuals with a strong family history of CHD than in those without such history. Shaukat et al., (1994) compared siblings (mean age 22 years) of South Asians and Europeans who had known CAD and discovered that the young Asians had lower levels of physical activity with more central obesity, insulin resistance, higher levels of Lp(a), and were developing a prothrombotic tendency with increased concentrations of plasminogen activator inhibitor-1 and decreased tissue plasminogen activator activity. More importantly, after adjusting for the levels of physical activity between the groups, the differences in insulin sensitivity and thrombotic tendency were smaller, whereas the Lp(a) was not affected. This also points toward a genetic tendency to higher Lp(a) levels. The limitations of this study are that the sample size was small (151), and the two group were equally randomized. The study also only surveyed rural areas so the findings cannot be generalised.
Total plasma homocysteine
When the essential amino acid methionine is metabolized, one of the products formed is total plasma homocysteine (tHcy). Homocysteine is a sulphur-containing amino acid and is further metabolized either by remethylation requiring vitamin B12 and folic acid or by a transulfuration pathway involving a vitamin B6–dependent enzyme (Rajeshwari et al., 2008). Homocysteine (Hcy) has been implicated as a novel risk factor of Coronary Artery Disease (CAD) among Indians in India (Abraham et al., 2006). Elevated plasma homocysteine can be due to various factors, such as: increased dietary intake, heritable enzyme deficiencies, and vitamin cofactor deficiencies (Scott, 1998). Abraham et al.'s 2006 case control study showed increased homocysteine levels among patients with coronary artery disease and also revealed an apparent correlation between low folate and high homocysteine. The values were not statistically significant as there is an inverse correlation between homocysteine and vitamin B12 which was not statistically significant; this may be because of the sample size, so the generalisability of the study could be limited
A few small studies have shown no relationship of homocysteine with CHD in India: for example, one study showed that homocysteine concentrations are not elevated in subjects with CAD and probably there is no association between total homocysteine and CAD in Indians (Snehalata et al., 2002). However, in Indians living in the UK, the homocystein concentrations observed were higher when compared to the European population (Chambers et al., 2000). It was estimated that elevated homocysteine may contribute to twice as many CHD deaths in Indians compared with Europeans. The differences in homocysteine concentrations between the two ethnic groups were explained by lower vitamin B12 and folate levels in the Indians. Hence, it could be suggested that dietary deficiencies or disorders related to folate and B12 malabsorption lead to hyperhomocysteinaemia and an increased risk of CAD (Abraham et al., 2006).
The following table summarizes the year of publication, the author, place of study, sample size, risk factors involved and key points of the studies that have been referenced in this section.
Therefore, the critical analysis above shows that, even though the sample sizes are small, there is consistent evidence that CHD among Indians is higher when compared to the British whites. These risk factors are the unique factors that differentiate the reason for increased CHD in India and other developed countries in the world. Hence, controlling these risk factors would reduce the epidemic of CHD in India.
Another factor that contributes to the risk for CHD is obesity. Obesity is considered as central obesity which measures the food patterns with metabolic risk factors for CHD. Ghosh et al. (2003) conducted a cross-sectional survey among middle aged (≥ 30 years) Bengali Hindu men in Calcutta, India. This study pinpointed the relationship between the central obesity measures and food pattern variables to explain the metabolic risk factors of CHD. The findings reported that body mass index (BMI) had no significant relation to any of the metabolic risk factors of CHD. However, almost all-central obesity measures, such as waist circumference (WC), waist-hip ratio (WHR), and conicity index (CI) were significantly related with TC, FTG, FPG and VLDL-c.
Regarding the food pattern variables, only the frequency of egg, fried snacks and Bengali sweets consumption were positively related with all central obesity measures, while chicken and fish consumption showed a negative association with central obesity. This study also found that the conicity index is the most consistent measure to identify and exemplify the metabolic variables of CHD. Comparing the urban and rural areas, again the urban areas had a higher incidence of obesity (14.5%) than rural areas in India (3%) (Gulati et al., 2004). The study does not mention the statistical analysis; this may be because of the word limit for publication.
Obesity, in particular abdominal obesity, is associated with decreased effects of insulin on peripheral glucose and glucose and fatty acid utilization. This situation ultimately leads to hyperinsulinemia and hyperglycemia and eventually increased atherosclerosis as it causes vascular endothelial dysfunction, dyslipidemia, hypertension, and vascular inflammation (Bedi et al., 2006). Insulin when it acts directly on the arterial walls helps synthesise lipids in the arterial tissues causing a proliferation of smooth muscle cells (Stout, 1990). Additionally, hyperinsulinemia and elevated triglyceride levels are associated with changes in the composition and size of particles in the low density lipoprotein fraction, which may be atherogenic (Austen et al., 1990).
Many case-control studies have found an association between insulin resistance and CHD (Lankisch et al., 2004; Snehalatha et al., 2001) and it is now considered an independent risk factor for the development of CHD as well as diabetes mellitus. McKeigue et al's (1991) study assessed the association of insulin resistance and CHD, finding that although smoking and cholesterol levels were lower in Indians when compared to Europeans, the incidence of CHD remained higher in the Indian population. The reason for this higher incidence was insulin resistance. Insulin resistance often precedes the onset of DM and already exists in the prediabetic states (Berry et al., 2007). Type 2 DM is a multifactorial disease that combines hereditary and environmental factors, but 80% of patients with type 2 DM are either obese or overweight (Kahn et al., 2000). Obesity and the metabolic syndrome are linked to hyperinsulinemia and insulin resistance and independently predict cardiovascular disease (CVD) and coronary atherosclerosis (Sowers, 2003). Hence, in other words it could be suggested that type 2 DM can be risk factor for CHD.
The only known environmental factors that affect insulin resistance are high dietary energy intake and lack of physical activity (Rajeshwari et al., 2008). Gulati et al.'s study suggests that the prevalence of diabetes was greater in urban areas (10.5%) than rural areas (3.5%). However this study fails to report the type of diabetes mellitus. Type 2 DM and related disorders in Indians overseas are probably consequences of low physical activity and high energy intake in populations adapted to survival under conditions of unreliable food supply and physically demanding work. If this hypothesis is correct, reduced energy intake and increased physical activity are likely to be the most effective means of preventing CVD in Indian populations [McKeigue, 1991].
Recent findings from the United Kingdom Prospective Diabetes Study (UKPDS) showed that among type 2 diabetes subjects the six modifiable risk factors were high concentration of LDL cholesterol, low concentration of HDL cholesterol, hypertension, hyperglycemia and smoking which are also the risk factors of CHD (Turner et al., 1998). Hence type 2 diabetes and CHD are linked with each other.
An observational study by Wilkinson et al. (1996), reported that admission rates for South Asians were 2.04 times higher than for British whites. The treatment was similar among the two ethnic groups, however South Asians received a higher proportion of thrombolytic drugs (81.2% v 73.8%). This study also showed that south Asians had a poorer survival rate over the six months from myocardial infarction and a substantially higher proportion of the patients were diabetic (38% v 11%). Additional treatment was done for diabetes as it removed much of their excess risk; hence the higher number of fatalities among the south Asians was largely attributable to diabetes, which may contribute to the increased risk of death from coronary heart disease in South Asians living in Britain. Hence, the high prevalence of diabetes, dyslipidaemia, and abdominal obesity clearly warrants intervention at the population and individual level (Ramraj and Chellappa, 2007).
Various studies have pointed to the fact that some components of metabolic syndrome, example, hyperinsulinemia, abdominal obesity, and
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