The findings stress the important role of higher BMI in the increasing rates of death from cardiovascular disease in Asia, which could be managed by policy and prevention strategies, say the authors.
Cardiovascular disease (CVD) is the leading cause of death globally and is predicted to steadily increase over the next few decades. Many Asian populations that used to be physically active with a low BMI now have some of the world's highest rates of obesity.
Studies of BMI and CVD risk have generally been conducted in Europe and North America and no data is available to compare east Asians (China, Taiwan, Singapore, Japan and Korea) and south Asians (India and Bangladesh) for any potential differences in the associations of BMI with CVD risk.
A group of international researchers therefore looked to evaluate the association between BMI and risk of death from overall cardiovascular disease, coronary heart disease and stroke in east and south Asians.
Generally, a BMI of 18.5 to 24.9 may indicate optimal weight, a BMI lower than 18.5 suggests the person is underweight, a number above 25 may indicate the person is overweight, and a number above 30 suggests the person is obese.
The research team used data on over 1.1 million men and women from the Asia Cohort Consortium (ACC), an international collaboration committed to the study of environmental exposures and genetics in the causes of disease.
Over a mean follow-up period of almost 10 years, the researchers identified 49,184 cardiovascular deaths (40,791 in east Asians and 8,393 in south Asians).
An increased risk of death was observed in all individuals with BMI values greater than 24.9 for overall cardiovascular disease, coronary heart disease and ischaemic stroke, compared with the reference BMI range (22.5-24.9), particularly in middle age.
This increased risk was stronger among individuals younger than 53 years - and was seen among never smokers, individuals free of cardiovascular disease at the start of the study, and individuals without high blood pressure (hypertension). For haemorrhagic stroke, the risk of death was higher at BMI values of 27.5 and above.
Elevated risk of death from cardiovascular disease was also observed at very low BMI ranges (less than 15 and 15-17.4), compared with the reference range.
In south Asians, the association was much less pronounced, with an increased risk of death from coronary heart disease observed only in individuals with a BMI greater than 35. The data also suggest no association between BMI and risk of death from stroke in south Asians.
The researchers conclude that the findings "stress the important role of higher BMI in the increasing rates of death from CVD in Asia, which could be managed by policy and prevention strategies." And they say additional research is needed "to better explain the elevated risk observed at low BMI and the apparently weak association among south Asians."