The Joint Associations of Sedentary Time and Physical Activity With Mobility Disability in Older People: The NIH-AARP Diet and Health Study

Abstract

Background: The purpose of this study was to determine the joint associations of sedentary time and physical activity with mobility disability in older age.

Methods: We analyzed prospective data from 134,269 participants in the National Institutes of Health (NIH)-American Association of Retired Persons (NIH-AARP) Diet and Health Study between 1995-1996 and 2004-2005. Total sitting time (h/d), TV viewing time (h/d) and light- and moderate-to-vigorous-intensity physical activity (h/wk) were self-reported at baseline, and mobility disability at follow-up was defined as being "unable to walk" or having an "easy usual walking pace (<2 mph)." Multivariable logistic regression determined the independent and joint associations of sedentary time and total physical activity with the odds of disability.

Results: Among the most active participants (>7 h/wk), sitting <6 h/d was not related to excess disability at follow-up, and those in the most active group reporting the highest level of sitting time (≥7 h/d) still had a significantly lower odds (odds ratios = 1.11; 95% confidence interval = 1.02, 1.20) compared with those reporting the lowest level of sitting (<3 h/d) in the least active group (≤3 h/wk; odds ratios = 2.07; 95% confidence interval = 1.92, 2.23). Greater TV time was significantly related to increased disability within all levels of physical activity.

Conclusions: Reduction of sedentary time, combined with increased physical activity may be necessary to maintain function in older age.

Figure 1.

Participant selection from the National Institutes of Health—American Association of Retired Persons (NIH-AARP) Diet and Health Study cohort. Those respondents who provided complete data on both questionnaires and who were free of chronic disease (eg, diabetes, heart disease, emphysema, cancer, or stroke) at baseline were eligible to be included in the analysis. To ensure the healthiest cohort possible, we also only included people who reported their health status as fair or better at baseline (N= 134,269).

Figure 2.

The joint association between daily sedentary time (h/d; a) or TV viewing time (h/d; b) and total physical activity (h/wk) on mobility disability in the National Institutes of Health—American Association of Retired Persons (NIH-AARP) Diet and Health Study cohort (N= 134,269). This joint analysis allowed us to compare directly groups with varying amounts of sedentary time and physical activity against those who sat the least and also had the most physical activity (referent group). Odds ratios (OR) and 95% confidence intervals (CI) are reported from the final logistic regression models to describe the excess odds of mobility disability within each level of sedentary time and physical activity relative to the referent group. All models were adjusted for age, sex, race, level of educational attainment, smoking, change in body mass index, as well as for reported health status at follow-up.