Elsevier

The Lancet

Volume 348, Issue 9024, 10 August 1996, Pages 358-363
The Lancet

Articles
Risk factors for acute myocardial infarction in Indians: a case-control study

https://doi.org/10.1016/S0140-6736(96)02507-XGet rights and content

Summary

Background

South Asians who have settled overseas and those in urban India have an increased risk of ischaemic heart disease (IHD). Reasons for this increased risk are unclear. Most studies have been based on migrants to western nations, so their findings may not apply to most south Asians, who live in their own countries. Therefore, we assessed the relative importance of risk factors for IHD among South Asians in Bangalore, India.

Methods

We conducted a prospective hospital-based case-control study of 200 Indian patients with a first acute myocardial infarction (AMI) and 200 age and sex matched controls. We recorded prevalence of the following risk factors for IHD: diet, smoking, alcohol use, socioeconomic status, waist to hip ratio (WHR), blood glucose, serum insulin, oral glucose tolerance test, and lipid profile.

Findings

The most important predictor of AMI was current smoking (odds ratio [OR] 3·6, p < 0·001) of cigarettes or beedis (a local form of tobacco), with individuals who currently smoked 10 or more per day having an OR of 6·7 (p < 0·001). History of hypertension and of overt diabetes mellitus were also independent risk factors (OR 2·69 [p=0·001] and 2·64 [p=0·004], respectively). Among all individuals, fasting blood glucose was a strong predictor of risk over the entire range, including at values usually regarded as normal (OR adjusted for smoking, hypertension, and WHR 1·62 for 1 SD increase, p < 0·001). Abdominal obesity (as measured by WHR) was also a strong independent predictor across the entire range of measures (OR adjusted for smoking, hypertension, and blood glucose 2·24 for 1 SD increase; p < 0·001). Compared with individuals with no risk factors, individuals with multiple risk factors had greatly increased risk of AMI (eg, OR of 10·6 for the group with smoking and elevated glucose). Lipid profile was not associated with AMI. In univariate analyses, higher socioeconomic (income) status (OR 0·32, p=0·005 highest vs lowest; OR 0·75 middle vs lowest) and vegetarianism (OR=0·55, p=0·006), seemed to be protective. The impact of vegetarianism was closely correlated with blood glucose and WHR.

Interpretation

Smoking cessation, treatment of hypertension, and reduction in blood glucose and central obesity (perhaps through dietary modification) may be important in preventing IHD in Asian Indians.

Introduction

Individuals of south Asian descent (India, Pakistan, and Bangladesh) have an increased risk of ischaemic heart disease (IHD) compared with most other ethnic groups. The reason for this increased risk, which has been recorded both among south Asian migrants to other countries1, 2 and among Indians in urban India,3, 4 is unclear. Prevalence of conventional risk factors such as smoking, hypertension, and hypercholesterolaemia is no higher in south Asians than in other ethnic groups.1, 5, 6, 7, 8 High triglyceride concentrations, low concentrations of high-density-lipoprotein (HDL) cholesterol, increased visceral fat, and insulin resistance are more prevalent among south Asians, and these factors have been proposed as reasons for the higher risk of IHD.1, 2, 6, 7, 9 However, a variable that is more common among south Asians may not necessarily be associated with IHD risk. Conversely, a factor that is not more common among south Asians may still have an important relation with IHD. Further, since most studies have been based on migrants to western countries, the findings may not necessarily apply to the vast majority of South Asians who live in their own countries. Therefore, we conducted a hospital-based case-control study of patients with a first myocardial infarction in Bangalore, India, to assess the relative importance of the risk factors for IHD among south Asians.

Section snippets

Cases

200 consecutive patients aged 30-60 years (inclusive) admitted to the coronary care unit of St John's Medical College Hospital with an acute myocardial infarction (AMI) were prospectively recruited as cases. AMI was defined as typical chest pain lasting at least 20 min and an electrocardiogram (ECG) showing ST elevation of at least 2 mm in two or more contiguous leads with subsequent evolution of the ECG and diagnostic enzyme changes (doubling of creatine kinase with at least 10% MB fraction).

Results

The demographic characteristics and lipid data of the 200 cases and 200 controls are shown in table 1. Cases had significantly lower monthly incomes than controls, and significantly fewer of them had a college education. The odds ratio (OR) for AMI was 0·32 (95% CI 0·16-0·66) for the highest versus lowest income group and 0·75 (0·48-1·17) for the middle versus lowest income groups.

Discussion

Our study, which is probably the first prospective case-control study aimed at identifying the relation between risk factors and AMI in south Asians in India, shows that tobacco smoking, a history of hypertension, a high prevalence of diabetes, increased fasting blood glucose (even in those who are not diabetic), and an increased ratio of visceral to total body fat (WHR) are independent risk factors for AMI. Patients with multiple risk factors have a substantially increased risk for AMI.

Our

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