A high BMI (> 30 kilograms/meter2) increases the risk of death from heart disease, stroke, and some cancers; however, questions remain about the strength of the relationship between high BMI and all-cause mortality, and optimal BMI in relation to mortality. These unanswered questions may be the result of methodological challenges related to population-based studies.
The BMI and All-Cause Mortality Pooling Project was a collaborative effort among more than 20 cohorts from the NCI Cohort Consortium to quantify the risk associated with being overweight or obese and the extent to which the relationship between BMI and all-cause mortality varies by factors such as age, sex, smoking status, pre-existing heart disease or cancer, physical activity, alcohol intake, education, and marital status. This Project systematically analyzed pooled data from prospective studies encompassing 1.46 million adults to estimate hazard ratios for the association between BMI and all-cause mortality.
The investigators published their results in the December 2, 2010 issue of the New England Journal of Medicine. They found that healthy women who had never smoked and who were overweight were 13 percent more likely to die during the study follow-up period than those with a BMI between 22.5 and 24.9. Women categorized as obese or severely obese had a dramatically higher risk of death. As compared with a BMI of 22.5 to 24.9, the researchers report a 44 percent increase in risk of death for participants with a BMI of 30.0 to 34.9; an 88 percent increase in risk for those with a BMI of 35.0 to 39.9; and a 2.5 times (250 percent) higher risk of death for participants whose BMI was 40.0 to 49.9. Results were broadly similar for men. Overall for men and women combined, for every five unit increase in BMI, the researchers observed a 31 percent increase in risk of death.