Body mass index and nine-year mortality in disabled and nondisabled older U.S. individuals.

Objectives: To investigate the relationship between body mass index (BMI) and 9-year mortality in older (> or = 65) Americans with and without disability.

Design: Cohort study.

Setting: The unique disability-focused National Long Term Care Survey (NLTCS) data that assessed the health and well-being of older individuals in 1994 were analyzed.

Participants: Four thousand seven hundred ninety-one individuals in the 1994 survey.

Measurements: BMI (kg/m2) was calculated from self- or proxy reports of height and weight. The analysis was adjusted for 1-year change in BMI and demographic and health-related factors, as well as reports by proxies, and death occurring during the first 2 years after the interview.

Results: The relative risk of death as a function of BMI formed a nonsymmetric U-shaped pattern, with larger risks associated with lower BMI (< 22.0) and minimal risks for BMI of 25.0 to 34.9. (BMI 22.0-24.9 was the reference.) Adjustments for demographic and health-related factors had little effect on this pattern. Nondisabled individuals exhibited a similar U-shaped pattern but with lower risks associated with lower BMI. For disabled individuals, the mortality-risk pattern was higher for lower BMI (< 22.0) and flat for higher BMI, thus exhibiting an inverse J shape. BMI patterns were age sensitive, with disability status affecting sensitivity.

Conclusion: Overweight or mild (grade 1) obesity was not a risk factor for 9-year mortality in older Americans participating in the 1994 NLTCS. A flatter BMI pattern of the relative risk of death for disabled than for nondisabled individuals suggests that optimal body weight can be sensitive to age and health and well-being.