The joint associations of weight status and physical activity with mobility disability: The NIH-AARP Diet and Health Study.

Abstract

The purpose of this study was to determine the joint associations of weight status and physical activity with mobility disability in older men and women. We analyzed prospective data from 135,220 participants in the NIH-AARP Diet and Health Study between 1995-1996 and 2004-2005. Height and weight, as well as light- and moderate-to-vigorous-intensity physical activity typical of the past 10 years (h/week) were self-reported at baseline, and body mass index (BMI: kg/m2) was categorized into normal weight (BMI 18 to <25 kg/m2); overweight (BMI 25 to <30 kg/m2); and obese (BMI ≥ 30 kg/m2). Mobility was assessed by self-report at follow-up and mobility disability was defined as reporting "unable to walk" or an "easy usual walking pace (<2 mph)". Multivariable logistic regression determined the independent and joint associations of weight status and total physical activity with the odds of mobility disability. Twenty-one percent of men and 37% of women reported a mobility disability at follow-up. We observed a curvilinear dose-response association between increasing categories of weight status and mobility disability within each tertile of physical activity, with the highest odds experienced by men and women with overweight (OR = 2.45; 95%CI: 2.25, 2.67 for men and OR = 2.99; 95%CI: 2.78, 3.22 for women) and obesity (OR = 3.93; 95%CI: 3.58, 4.32 for men and OR = 5.08; 95% CI: 4.65, 5.54 for women) in combination with low physical activity. Moreover, among those reporting 7 or fewer hours/week of total physical activity, being of normal body weight did not eliminate the excess odds of mobility disability. These findings highlight the combined importance of obesity prevention and physical activity promotion to mobility in older age. Given aging demographics and the global economic burden associated with aging- and disuse-related disability, there is tremendous public health benefit to understanding how various modifiable determinants of mobility disability can interact in older age.