Body mass index and mortality in middle-aged Korean women

PURPOSE: We sought to evaluate the association between body mass index (BMI) and mortality in Korean women and to determine whether the association differs depending on menopausal status. METHODS: A total of 338,320 Korean women ages 40 to 64 years categorized into seven groups by BMI level were prospectively followed for mortality from approximately 1994 to 2004. RESULTS: Multivariable-adjusted analysis using Cox proportional hazards model showed a U-shaped association between BMI and all-cause deaths, with the lowest risk at BMI between approximately 25 and 26.9 kg/m2, even after excluding earlier deaths, which did not change when we did a stratified analysis according to menopausal status. A U-shaped association was observed between BMI and cancer death, and the risk associated with low BMI decreased significantly after excluding earlier cancer deaths. There was a J-shaped association between BMI and coronary heart disease (CHD) with a significantly increased risk at greater BMI (>26 kg/m2). Additional adjustment for possible biological effects of obesity (i.e., serum total cholesterol, glucose, and systolic blood pressure) changed the U-shaped association between BMI and all-causes mortality into an inverse shape and substantially reduced the size of risk for CHD death associated with high BMI level. In stratified analysis, the association between BMI and CHD was positive linear in women at premenopausal status, whereas it was U-shaped in women at postmenopausal status. CONCLUSIONS: Obesity was associated with an increased risk of mortality in both premenopausal and postmenopausal Korean women, indicating that preventive strategies to control obesity are important even in population with a relatively low mean BMI level.