The Asian Cohort Consortium (ACC) including Dr. Yuan-Tsong Chen and Dr. Chen-Yang Shen, principal investigators at the Taiwan Biobank and the Institute of Biomedical Sciences, Academia Sinica, as well as researchers from several countries including Japan, Korea, China, Singapore and India, recently found that underweight is significantly associated with increased risk of death across Asia, while high body mass index (BMI) is associated with a higher risk of death only in East Asian populations. The study, which pooled data from more than 1.1 million people, was reported in the February 24, 2011 issue of The New England Journal of Medicine.

The researchers explored the correlation between Body Mass Index (BMI), an index of obesity, and mortality in 19 Asian cohorts over an average of 9.2 years. They found that mortality was lowest among people with a BMI in the range of 22.6 to 27.5. The risks were significantly higher among people with BMI levels either higher or lower than that range – increasing by a factor of up to 1.5 among those with a BMI 35.0 and by a factor of 2.8 among those with a BMI of 15.0 or less. A similar U-shaped association was also seen between BMI and mortality due to cancer, cardiovascular diseases, and other causes of death. High BMI was not, however, found to be associated with higher risk of death in Indian and Bangladeshi cohorts.

Up until now most studies exploring the association between BMI and mortality have been conducted in populations of European origin. The ACC study aimed to evaluate the same association between BMI and mortality, specifically in an Asian population. The study is one of the largest of its kind in the world and the findings are expected to impact public health policy in Asian countries and provide essential and critical information for implementing public weight control programs in Taiwan.

The research was supported by Dr. Chien-Jen Chen and Dr. San-Lin You from the Genomics Research Center, and Dr. Wen-Harn Pan from the Institute of Biomedical Sciences. This joint effort by members of the ACC across Asia has demonstrated the value of international cooperation in scientific research. In addition, the study highlights the importance of the Taiwan Biobank, a large population-based cohort database funded by the Department of Health and housed at Academia Sinica that combines genetic and other medical information about the Taiwan population to aid in the study of local common diseases.

The investigators concluded that "overall, the risk of death among Asians, as compared with Europeans, seems to be more strongly affected by a low BMI than by a high BMI". They noted, however, that their study did not address the impact of abdominal obesity on risk of death, which they say "may be a particularly important factor in Asian populations."

The full text entitled "Association between Body-Mass Index and Risk of Death in More Than 1 Million Asians" is available at New England Journal of Medicine website at http://www.nejm.org/doi/full/10.1056/NEJMoa1010679