High body mass index does not predict mortality in older people: Analysis of the Longitudinal Study of Aging

OBJECTIVE: To determine the excess mortality associated with obesity (defin ed by body mass index (BMI)) in older people, with and without adjustment f or other risk factors associated with mortality and for demographic factors . DESIGN: Retrospective cohort analysis of the Longitudinal Study of Aging (L SOA). SETTING: Nationally representative sample of community-dwelling older peopl e. PARTICIPANTS: Seven thousand five hundred and twenty-seven participants age 70 and older in 1984. MEASUREMENTS: We used Cox regression to calculate proportional hazards rati os for mortality over 96 months. We tested the hypothesis that increased BM I (top 15 %) increased mortality rates in older people. RESULTS: Death occurred in 38% of the cohort: 54% of the thin (lowest 10% o f the population, BMI < 19.4 kg/m(2)), 33% of the obese (highest 15%, BMI > 28.5 kg/m(2)), and 37% of the remaining participants (normal) died. Adjust ment for demographic factors, health services utilization, and functional s tatus still demonstrated reduced mortality in obese older people (hazard ra tio 0.86, 95% confidence interval (CI) = 0.77-0.97) compared with normal. A fter adjustment, thin older people remained more likely to die (hazard rati o 1.46, 95% CI = 1.30-1.64) than normal older people. Sensitivity analyses for income, mortality during the first two years of follow-up, and medical comorbidities did not substantively alter the conclusions. CONCLUSION: Obesity may be protective compared with thinness or normal weig ht in older community-dwelling Americans.