THE EFFECT OF AGE ON THE ASSOCIATION BETWEEN BODY-MASS INDEX AND MORTALITY

Background The effect of age on optimal body weight is controversial, and few studies have had adequate numbers of subjects to analyze morta lity as a function of body-mass index across age groups. Methods We st udied mortality over 12 years among white men and women who participat ed in the American Cancer Society's Cancer Prevention Study I (from 19 60 through 1972). The 62,116 men and 262,019 women included in this an alysis had never smoked cigarettes, had no history of heart disease, s troke, or cancer (other than skin cancer) at base line in 1959-1960, a nd had no history of recent unintentional weight loss. The date and ca use of death for subjects who died were determined from death certific ates. The associations between body-mass index (defined as the weight in kilograms divided by the square of the height in meters) and mortal ity were examined for six age groups in analyses in which we adjusted for age, educational level, physical activity, and alcohol consumption . Results Greater body-mass index was associated with higher mortality from all causes and from cardiovascular disease in men and women up t o 75 years of age. However, the relative risk associated with greater body-mass index declined with age. For example, for mortality from car diovascular disease, the relative risk associated with an increment of 1 in the body-mass index was 1.10 (95 percent confidence interval, 1. 04 to 1.16) for 30-to-44-year-old men and 1.03 (95 percent confidence interval, 1.02 to 1.05) for 65-to-74-year-old men. For women, the corr esponding relative risk estimates were 1.08 (95 percent confidence int erval, 1.05 to 1.11) and 1.02 (95 percent confidence interval, 1.02 to 1.03). Conclusions Excess body weight increases the risk of death fro m any cause and from cardiovascular disease in adults between 30 and 7 4 years of age. The relative risk associated with greater body weight is higher among younger subjects. (C) 1998, Massachusetts Medical Soci ety.