Obesity, race, and risk for death or functional decline among Medicare beneficiaries: a cohort study.

BACKGROUND: The adverse effect of obesity on health outcomes may be lower in older and African American adults than in the general U.S. population.
OBJECTIVE: To examine and compare the relationship between obesity and all-cause mortality and functional decline among older U.S. adults.
DESIGN: Longitudinal cohort study.
SETTING: Secondary analysis of data from the 1994 to 2000 Medicare Current Beneficiary Surveys, linked to Medicare enrollment files through 22 April 2008. PARTICIPANTS: 20,975 community-dwelling participants in the 1994 to 2000 Medicare Current Beneficiary Surveys who were aged 65 years or older. MEASUREMENTS: All-cause mortality through 22 April 2008; new or worsening disability in performing activities of daily living (ADLs) and instrumental activities of daily living (IADLs) in 2 years.
RESULTS: 37% of the study sample were overweight (body mass index [BMI] of 25 to <30 kg/m(2)), 18% were obese (BMI ≥30 kg/m(2)), 48% died during the 14-year follow-up, and 27% had ADL and 43% had IADL disability at baseline. Among those without severe disability at baseline, 17% developed new or worsening ADL disability and 26% developed new or worsening IADL disability within 2 years. After adjustment, adults with a BMI of 35 kg/m(2) or greater were the only group above the normal BMI range who had a higher risk for mortality (hazard ratio, 1.49 [95% CI, 1.20 to 1.85] in men and 1.21 [CI, 1.06 to 1.39] in women, compared with the reference group [BMI of 22.0 to 24.9 kg/m(2)]; P for BMI-sex interaction = 0.003). In contrast, both overweight and obesity were associated with new or progressive ADL and IADL disability in a dose-dependent manner, particularly for white men and women. Significant interactions were detected between BMI and sex but not between BMI and race for any outcome, although risk estimates for ADL disability seemed attenuated in African American relative to white respondents. LIMITATION: This was an observational study, baseline data were self-reported, and the study had limited power to detect differences between white and African American respondents.
CONCLUSION: Among older U.S. adults, obesity was not associated with mortality, except for those with at least moderately severe obesity. However, lower levels of obesity were associated with new or worsening disability within 2 years. Efforts to prevent disability in older adults should target those who are overweight or obese. PRIMARY FUNDING SOURCE: National Institute of Diabetes and Digestive and Kidney Diseases.