Body Mass Index, Weight Change, and Risk of Mobility Disability in Middle-aged and Older Women

OBJECTIVE: As disability is highly prevalent among older women, is costly, and affects the quality of life, preventable causes of disability must be identified. In this study, we investigated the relationship between the body mass index (BMI), weight change, and the onset of disability in older women. DESIGN: Prospective cohort study. SETTING: The nationally representative US epidemiologic follow-up study of the National Health and Nutrition Examination Survey (NHANES) I (1971 through 1987). PATIENTS: White women classified as young-old (mean age 60 years at baseline, mean age 65 years at follow-up) and old-old (mean age 76 years at baseline, mean age 80 years at follow-up). MAIN OUTCOME MEASURES: The relative odds for the onset of mobility disability associated with tertiles of past BMI (measured 8 to 16 years prior to disability ascertainment) and current BMI (measured 2 to 5 years prior to disability ascertainment) and with weight change between the two weight measurements. RESULTS: In both cohorts, women in the high past BMI group (> 27 in the young-old and > 28.1 in the old-old cohort) had a twofold increase in the risk for disability compared with women in the low past BMI group. High current BMI was as strongly related as past BMI to risk of disability in the young-old women; it was not as strong a predictor in old-old women. In the old-old group only, women who experienced a weight loss of more than 5% had a twofold increase in risk of disability compared with weight-stable women. These results were adjusted for age, smoking, education, and study time and were not importantly modified with the addition into the models of single or multiple health conditions. CONCLUSIONS: These prospective data suggest that high BMI is a strong predictor of long-term risk for mobility disability in older women and that this risk persists even to very old age. However, the paradoxical increase in risk associated with weight loss in the old-old women requires further study. Programs to prevent overweight may have potential for decreasing disability in women.