Increase in body mass index category since age 20 years and all-cause mortality: a prospective cohort study (the Ohsaki Study).

BACKGROUND: It is still unclear whether weight gain from early to late adulthood affects longevity. Furthermore, no study has addressed its association with all-cause and cause-specific mortality in an Asian population.

METHODS: We prospectively assessed the association between an increase in body mass index (BMI) category since age 20 years and risk of all-cause, cardiovascular disease (CVD) and cancer mortality. Self-reported information pertaining to BMI was collected from 38 080 Japanese men and women aged 40-79 years at study entry in 1994 after exclusion of participants with a BMI of <18.5 kg/m(2) at age 20 years or at study entry. We defined six patterns of increase in BMI category at age 20 years and study entry: stable normal, overweight and obese, normal to overweight or obese, and overweight to obese.

RESULTS: During 7 years of follow-up, 2617 participants died. After adjustment for potential confounders, we observed a significantly increased risk of all-cause mortality for the pattern of normal weight at age 20 years and obese at study entry and of stable obese compared with stable normal in BMI category, the multivariate HRs (95% confidence interval (CI)) being 1.42 (1.08-1.88) and 2.26 (1.45-3.51), respectively. For the pattern of overweight at age 20 years and obese at study entry, the multivariate hazard ratio (95% CI) was 1.35 (0.92-1.98). In contrast, we did not observe an increased risk of all-cause mortality for normal weight at age 20 years and overweight at study entry, and stable overweight. For CVD and cancer mortality, these results were consistently observed.

CONCLUSION: We observed an increased risk of all-cause mortality both among participants who had been persistently obese since early adulthood and participants who showed an increase in BMI category from normal to obese, compared with participants with a stable normal BMI category.