Mortality Benefits for Replacing Sitting Time with Different Physical Activities

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(-1)) was associated with increased risk for all-cause and cardiovascular mortality. In less active adults (<2 h·d(-1) total activity), replacing 1 h·d(-1) 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(-1) 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.

Trial registration: ClinicalTrials.gov NCT00340015.

Figure 1

Duration (hrs/d) of overall physical activity (Panel A) and sitting time (Panel B), by type of behavior and sex, the NIH-AARP Diet and Health Study Values are mean and SD, and % total activity reported

Figure 2

Association* between all-cause mortality and exercise and non-exercise activity estimated by restricted cubic splines, by sex, the NIH-AARP Diet and Health Study *Values are Hazard Ratios and 95% Confidence Intervals adjusted for Age (years), Education (< 12 yrs, high school graduate, some college, college graduate, unknown), Smoking history (never, stopped 10+, stopped 5–9, stopped 1–4 years, stopped < 1 year, current smoker, unknown), Sleep duration (< 4, 4–5.9, 6–7.9, 8–9.9, 10+ hours/day, unknown), Overall health (excellent, very good, good, fair, poor, unknown), and Body Mass Index (< 25, 25–29.9, 30+ kg/m², unknown), Overall sitting (hrs/d), and the other type of physical activity. To fit the splines knots were placed at intervals of 0.5 to 1 hrs/d increments over the range of each exposure and data were trimmed at approximately the 95^th percentile of each exposure distribution. Exercise activities include: walking for exercise; jogging or running; racquet sports; playing golf; swimming laps; bicycling or stationary bike; other aerobic exercise; weight training or lifting Non-exercise activities include: light household chores; moderate-vigorous indoor household chores; moderate outdoor chores; vigorous outdoor chores; home repairs; caring for children, caring for adults, walking for daily activities

Figure 3

Estimated risk* for all-cause mortality associated with replacement of one hour of overall sitting with an equal amount of time in specific types and intensities of physical activity, in less and more active participants, the NIH-AARP Diet and Health Study. *Values are Hazard Ratios and 95% Confidence Intervals adjusted for Age (years), Education (< 12 yrs, high school graduate, some college, college graduate, unknown), Smoking history (never, stopped 10+, stopped 5–9, stopped 1–4 years, stopped < 1 year, current smoker, unknown), Sleep duration (< 4, 4–5.9, 6–7.9, 8–9.9, 10+ hours/day, unknown), Overall health (excellent, very good, good, fair, poor, unknown), and Body Mass Index (< 25, 25–29.9, 30+ kg/m2, unknown), and Overall sitting (hrs/d) each type of Physical Activity (hrs/d), and the sum of Overall Sitting and Physical Activity time (hrs/d) Exercise activities include: walking for exercise; jogging or running; racquet sports; playing golf; swimming laps; bicycling or stationary bike; other aerobic exercise; weight training or lifting Non-exercise activities include: light household chores; moderate-vigorous indoor household chores; moderate outdoor chores; vigorous outdoor chores; home repairs; caring for children, caring for adults, walking for daily activities Household chores include: light household chores; moderate-vigorous indoor household chores; home repairs; caring for children, caring for adults Lawn and garden activities include: moderate outdoor chores; vigorous outdoor chores Daily walking (non-exercise) includes: walking for daily activities Light activities include: light household chores; walking for daily activities Moderate-vigorous activities include: walking for exercise; jogging or running; racquet sports; playing golf; swimming laps; bicycling or stationary bike; other aerobic exercise; weight training or lifting; moderate-vigorous indoor household chores; moderate outdoor chores; vigorous outdoor chores; home repairs; caring for children, caring for adults