Body mass index at age 25 and all-cause mortality in whites and African Americans: the Atherosclerosis Risk in Communities study

Abstract

Purpose: Approximately 20% of young adults in the United States are obese, and most of them gain weight between young and middle adulthood. Few studies have examined the association between elevated body mass index (BMI) in early adulthood and mortality or have examined that such effects are independent of changes in weight. To our knowledge, no such study has been conducted in African-American samples.

Methods: We used data from 13,941 African-American and white adults who self-reported their weight at the age of 25, and had weight and height measured when they were 45-64 years of age (1987-1989). Date of death was ascertained between 1987 and 2005. Hazard ratios and hazard differences for the effects of BMI at age 25 on all-cause mortality were determined using Cox proportional hazard and additive hazard models, respectively.

Results: In the combined ethnic-gender groups, the hazard ratio associated with a 5 kg/m(2) increase in BMI at age 25 was 1.28 (95% confidence interval [CI]: 1.22-1.35), and the hazard difference was 2.75 (2.01-3.50) deaths/1,000 person-years. Associations were observed in all four ethnic-gender groups. Models including weight change from age 25 to age in 1987-1989 resulted in null estimates for BMI in African-American men, whereas associations were maintained or only mildly attenuated in other ethnic-gender groups.

Conclusions: Excess weight during young adulthood should be avoided because it contributes to increases in death rates that may be independent of changes in weight experienced in later life. Further study is needed to better understand these associations in African-American men.

Figure 1

Adjusted hazard ratios for mortality by weight status category (at age 25) overall and by ethnic-gender group. Models were adjusted for smoking status at age 25 and age, education, field center, smoking status, physical activity, alcohol consumption and height at visit 1. Overall model also adjusted for gender and race. Open symbols are from models not adjusted for weight change. Closed symbols are from models adjusted for weight change (measured weight at visit 1 minus self-reported weight at age 25 and modeled using a quadratic spline function with 5 knots).

Figure 2

Adjusted hazard differences per 1,000 person-years for mortality by weight status category (at age 25) overall and by ethnic-gender group. Models were adjusted for smoking status at age 25 and age, education, field center, smoking status, physical activity, alcohol consumption and height at visit 1. Overall model also adjusted for gender and race. Open symbols are from models not adjusted for weight change. Closed symbols are from models adjusted for weight change (measured weight at visit 1 minus self-reported weight at age 25 and modeled using a quadratic spline function with 5 knots).