Relative weight and mobility: A longitudinal study in a biracial population of older adults

PURPOSE: We examined the association of relative weight with mobility and changes in mobility over time and whether these associations differed by race. METHODS: Data come from a prospective, population-based, observational study of adults aged 65 years or older. Mobility outcomes were assessed at baseline and two follow-up interviews at 3-year intervals. The study included 4195 participants with a mean age of 73.8 +/- 6.3 (SD) years; 61.4% were women, and 60.9% were black. Assessment of mobility included a brief self-report instrument and a performance-based walk test. Body mass index (BMI, kilograms per square meter) was used as a measure of relative weight. We used generalized estimating equation models to examine change in mobility outcomes over time as a function of BMI. RESULTS: Average BMI was 26.6 +/- 5.7 kg/m(2), with 34.0% overweight and 23.4% obese. BMI showed a significant curvilinear association with mobility outcomes at baseline (p < 0.001), but was not associated with change in mobility during follow-up. Maximum mobility levels occurred at a significantly higher level of BMI among blacks than whites. CONCLUSIONS: Higher levels of BMI may lead to mobility impairments earlier in life, but there is little evidence that they increase the rate of decline in mobility in older age itself.