MORTALITY AND OPTIMAL BODY-MASS INDEX IN A SAMPLE OF THE US POPULATION

In this paper, the authors model the nonmonotonic relation between bod y mass index (BMI) (weight (kg)/height(2) (m(2))) and mortality in 13, 242 black and white participants in the NHANES I Epidemiologic Follow- up Study in order to estimate the BMI at which minimum mortality occur s. The BMI of minimum mortality was 27.1 for black men (95% confidence interval (CI) 24.8-29.4), 26.8 for black women (95% CI 24.7-28.9), 24 .8 for white men (95% CI 23.8-25.9), and 24.3 for white women (95% CI 23.3-25.4). Each confidence interval included the group average. Analy ses conducted by smoking status and after exclusion of persons with ba seline illness and persons who died during the first 4 years of follow -up led to virtually identical estimates. The authors determined the r ange of values over which risk of all-cause mortality would increase n o more than 20% in comparison with the minimum. This interval was nine BMI units wide, and it included 70% of the population. These results were confirmed by parallel analyses using quantiles. The model used al lowed the estimation of parameters in the BMI-mortality relation. The resulting empirical findings from each of four race/sex groups, which are representative of the US population, demonstrate a wide range of B MIs consistent with minimum mortality and do not suggest that the opti mal BMI is at the lower end of the distribution for any subgroup.