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.