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

Background/objectives: 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.

Subjects/methods: We analyzed prospective data from 135,220 participants in the NIH-AARP Diet and Health Study between 1995-1996 and 2004-2005.

Methods: 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.

Results: 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.

Conclusions: 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.