Replacing Sitting Time With Different Physical Activities
Replacing Sitting Time With Different Physical Activities
Purpose: Prolonged sitting has emerged as a risk factor for early mortality, but the extent of benefit realized by replacing sitting time with exercise or activities of everyday living (i.e., nonexercise activities) is not known.
Methods: We prospectively followed 154,614 older adults (59–82 yr) in the National Institutes of Health-AARP Diet and Health Study who reported no major chronic diseases at baseline and reported detailed information about sitting time, exercise, and nonexercise activities. Proportional hazard models were used to estimate adjusted hazard ratios and 95% confidence intervals (HR (95% confidence interval)) for mortality. An isotemporal modeling approach was used to estimate associations for replacing sitting time with specific types of physical activity, with separate models fit for less active and more active participants to account for nonlinear associations.
Results: During 6.8 yr (SD, 1.0) of follow-up, 12,201 deaths occurred. Greater sitting time (≥12 vs < 5 h·d) was associated with increased risk for all-cause and cardiovascular mortality. In less active adults (<2 h·d total activity), replacing 1 h·d of sitting with an equal amount of activity was associated with lower all-cause mortality for both exercise (HR, 0.58 (0.54–0.63)) and nonexercise activities (HR, 0.70 (0.66–0.74)), including household chores, lawn and garden work, and daily walking. Among more active participants (2+ h·d total activity), replacement of sitting time with purposeful exercise was associated with lower mortality (HR, 0.91 (0.88–0.94)) but not with nonexercise activity (HR, 1.00 (0.98–1.02)). Similar results were noted for cardiovascular mortality.
Conclusions: Physical activity intervention strategies for older adults often focus on aerobic exercise, but our findings suggest that reducing sitting time and engaging in a variety of activities is also important, particularly for inactive adults.
In modern societies that have largely engineered obligatory physical activity out of daily life, encouraging participation in moderate-to-vigorous aerobic exercise has been a key public health strategy for reducing the risk for noncommunicable diseases and early mortality. However, recent studies have challenged the idea that a few hours per week of aerobic exercise alone is sufficient to fully mitigate mortality risks associated with the many hours that adults spend in sedentary behavior. In part, this may reflect that elevated health risks associated with excessive sitting arise from the displacement of daily routine activities by sitting behaviors. Activities typically displaced by prolonged sitting include daily activities like household chores (e.g., cooking, cleaning, shopping) and moderate-to-vigorous activities not typically classified as aerobic exercise (e.g., vacuuming, sweeping, mowing, gardening). We refer to such behaviors as nonexercise physical activities to distinguish them from exercise done for health and fitness and from sedentary time. Implicit in the displacement hypothesis is that replacing sitting time with physically active behaviors will be associated with lower disease risk. However, few studies have estimated the mortality benefits associated with replacement of sitting time with an equal amount of time in either purposeful exercise or other nonexercise activities.
In this report, we extend our earlier finding that excessive sedentary time was associated with greater mortality and, using more detailed measurements of physical activity and sitting time, we estimate the mortality benefits associated with replacement of sitting time with different types of physical activity. To do so, we are among the first to use a novel isotemporal modeling approach that facilitates investigation of the mortality trade-offs between spending time in either sedentary behavior or physical activity. Clarifying the types of physical activity that are healthful alternatives to sitting is critical for the development of evidenced-based recommendations for reducing sedentary time and increasing physical activity, and because results from randomized trials of sedentary time and mortality are unavailable, prospective observational studies provide essential insights.
Abstract and Introduction
Abstract
Purpose: Prolonged sitting has emerged as a risk factor for early mortality, but the extent of benefit realized by replacing sitting time with exercise or activities of everyday living (i.e., nonexercise activities) is not known.
Methods: We prospectively followed 154,614 older adults (59–82 yr) in the National Institutes of Health-AARP Diet and Health Study who reported no major chronic diseases at baseline and reported detailed information about sitting time, exercise, and nonexercise activities. Proportional hazard models were used to estimate adjusted hazard ratios and 95% confidence intervals (HR (95% confidence interval)) for mortality. An isotemporal modeling approach was used to estimate associations for replacing sitting time with specific types of physical activity, with separate models fit for less active and more active participants to account for nonlinear associations.
Results: During 6.8 yr (SD, 1.0) of follow-up, 12,201 deaths occurred. Greater sitting time (≥12 vs < 5 h·d) was associated with increased risk for all-cause and cardiovascular mortality. In less active adults (<2 h·d total activity), replacing 1 h·d of sitting with an equal amount of activity was associated with lower all-cause mortality for both exercise (HR, 0.58 (0.54–0.63)) and nonexercise activities (HR, 0.70 (0.66–0.74)), including household chores, lawn and garden work, and daily walking. Among more active participants (2+ h·d total activity), replacement of sitting time with purposeful exercise was associated with lower mortality (HR, 0.91 (0.88–0.94)) but not with nonexercise activity (HR, 1.00 (0.98–1.02)). Similar results were noted for cardiovascular mortality.
Conclusions: Physical activity intervention strategies for older adults often focus on aerobic exercise, but our findings suggest that reducing sitting time and engaging in a variety of activities is also important, particularly for inactive adults.
Introduction
In modern societies that have largely engineered obligatory physical activity out of daily life, encouraging participation in moderate-to-vigorous aerobic exercise has been a key public health strategy for reducing the risk for noncommunicable diseases and early mortality. However, recent studies have challenged the idea that a few hours per week of aerobic exercise alone is sufficient to fully mitigate mortality risks associated with the many hours that adults spend in sedentary behavior. In part, this may reflect that elevated health risks associated with excessive sitting arise from the displacement of daily routine activities by sitting behaviors. Activities typically displaced by prolonged sitting include daily activities like household chores (e.g., cooking, cleaning, shopping) and moderate-to-vigorous activities not typically classified as aerobic exercise (e.g., vacuuming, sweeping, mowing, gardening). We refer to such behaviors as nonexercise physical activities to distinguish them from exercise done for health and fitness and from sedentary time. Implicit in the displacement hypothesis is that replacing sitting time with physically active behaviors will be associated with lower disease risk. However, few studies have estimated the mortality benefits associated with replacement of sitting time with an equal amount of time in either purposeful exercise or other nonexercise activities.
In this report, we extend our earlier finding that excessive sedentary time was associated with greater mortality and, using more detailed measurements of physical activity and sitting time, we estimate the mortality benefits associated with replacement of sitting time with different types of physical activity. To do so, we are among the first to use a novel isotemporal modeling approach that facilitates investigation of the mortality trade-offs between spending time in either sedentary behavior or physical activity. Clarifying the types of physical activity that are healthful alternatives to sitting is critical for the development of evidenced-based recommendations for reducing sedentary time and increasing physical activity, and because results from randomized trials of sedentary time and mortality are unavailable, prospective observational studies provide essential insights.