Increases in body mass index over a 7-year period and risk of cause-specific mortality in Korean men

Background: The association between increased body mass index (BMI) and subsequent mortality remains unclear in Asians. This study investigated the associations between BMI increases and cause-specific mortality in middle-aged Korean men. Methods: We conducted a retrospective cohort study of 473 358 Korean men aged 30-64 years, who had undergone health examinations in both 1992 and 1998 and were followed up during 1998-2004. Cox proportional hazards for cause-specific 7-year mortality in relation to BMI changes after stratification of baseline BMI status were analysed. Results: Mortality from cardiovascular disease (CVD) was associated with BMI in both 1992 and 1998. Non-CVD mortality was inversely associated with BMI in both 1992 and 1998. We cross-classified participants into groups based on their baseline BMI levels and percent BMI changes during follow-up; men with the lowest BMI level at baseline (BMI in 1992 <21 kg/m²) and stable BMI during follow-up (percent change in BMI <5%) were included in the reference category. Compared with the reference group, CVD mortality was higher in initially obese men (BMI in 1992 525 kg/m²) with any increase of BMI, and in initially lean men (BMI in 1992 <21 kg/m²) or initially overweight men (BMI in 1992 23-24.9 kg/m²) with BMI increases of510%. BMI increases of 5.0-9.9% in men with baseline BMI <25 kg/m² and stable BMI in men with baseline BMI 521 kg/m² appeared to lower the risk for non-CVD or all-cause mortality, to below the levels seen in the reference group. Conclusions Among middle-aged Korean men, obesity or severe weight gain was detrimental to CVD mortality. An increase in BMI appeared to have a predictive value for CVD mortality, especially when used in combination with baseline BMI level. In contrast, moderate weight gain in non-obese men seemed to protect against non-CVD and all-cause mortality.