Purpose We examined total, light, and moderate-to-vigorous physical activity (MVPA) as predictors of mortality in a nationally representative sample of older adults. Then, we explored the theoretical consequences of replacing sedentary time with the same duration of light activity or MVPA. Methods Using accelerometer measured activity, the associations between total, light (100 to 2019 counts per minute), and moderate-to-vigorous (>2019 counts per minute) activity counts and mortality were examined in adults aged 50 to 79 in the National Health and Nutrition Examination Survey, 2003-2006 (n=3,029), with mortality follow-up through December 2011. Cox proportional hazards models were fitted to estimate mortality risks. An isotemporal substitution model was used to examine the theoretical consequences of replacing sedentary time with light activity or MVPA on mortality. Results After adjusting for potential confounders, including age, sex, race/ethnicity, education, body mass index, and the presence of comorbid conditions, those in the highest tertile of total activity counts had one fifth the risk of death of those in the lowest tertile (HR: 0.21, 95% CI: 0.12, 0.38), and those in the middle tertile had one third the risk of death (HR: 0.36, 95% CI: 0.30, 0.44). In addition, replacing thirty minutes of sedentary time with light activity was associated with significant reduction in mortality risk (After 5 years of follow-up: HR = 0.80, 95% CI: 0.75, 0.85). Replacing thirty minutes of sedentary time with MVPA was also associated with reduction in mortality risk (HR = 0.49, 95% CI: 0.25, 0.97). Conclusions Greater total activity is associated with lower all-cause mortality risk. Replacing sedentary time with light activity or MVPA may reduce mortality risk for older adults.

Across all waking hours of 1 d, step counts differ between devices. The SW, regardless of settings, was the most accurate method of counting steps.

Background Inactivity and sedentary behavior are related to poorer health outcomes in breast cancer survivors. However, few studies examining these behaviors in survivors have used objective measures, considered activities other than moderate-to-vigorous intensity activity (MVPA) and/or sedentary behavior (i.e. low intensity activities) or compared survivors to healthy controls. The purpose of the present study is to compare accelerometer-measured activity of various intensities (total, light, lifestyle, MVPA) and sedentary behavior between breast cancer survivors and non-cancer controls. Methods An imputation-based approach of independent sample t-tests adjusting for multiple comparisons was used to compare estimates of participation in each activity and sedentary behavior between survivors [n=398; M(SD)age=56.95 (9.11)] and block-matched non-cancer controls [n=1120; M(SD)age=54.88 (16.11)]. Potential moderating effects of body mass index (BMI), age, and education were also examined. Results Breast cancer survivors registered less daily total (282.8 v. 346.9) light (199.1 v. 259.3) and lifestyle (62.0 v. 71.7) activity minutes and more MVPA (21.6 v. 15.9) and sedentary behavior (555.7 v. 500.6) minutes than controls (p<0.001 for all). These relationships were largely consistent across BMI, age and education. On average, survivors spent an estimated 66.4% of their waking time sedentary and 31.1% in light/lifestyle activity and 2.6% in MVPA. Conclusions Breast cancer survivors are more sedentary and participate in less low intensity activity than controls. Although survivors registered more MVPA, these levels were insufficient. Future research should explore these differences and potential benefits of targeting low intensity activities and reducing sedentary time in this population.

Differences in data processing algorithms may have resulted in the observed disagreement in posture and activity classification between thigh-worn ActiGraph and activPAL. Despite between-monitor agreement in classifying sitting time under free-living conditions, ActiGraph appears to be more sensitive to free-living upright walking motions than activPAL.

BackgroundAn individual’s occupational activity (OA) may contribute significantly to daily physical activity (PA) and sedentary behavior (SB). However, there is little consensus about which occupational categories involve high OA or low OA, and the majority of categories are unclassifiable with current methods. The purpose of this study was to present population estimates of accelerometer-derived PA and SB variables for adults (n = 1112, 20–60 years) working the 40 occupational categories collected during the 2003–2004 National Health and Nutrition Examination Survey (NHANES).MethodsActiGraph accelerometer-derived total activity counts/day (TAC), activity counts/minute, and proportion of wear time spent in moderate-to-vigorous PA [MVPA], lifestyle, and light PA organized by occupational category were ranked in ascending order and SB was ranked in descending order. Summing the ranks of the six accelerometer-derived variables generated a summary score for each occupational category, which was re-ranked in ascending order. Higher rankings indicated higher levels of OA, lower rankings indicated lower levels of OA. Tertiles of the summary score were used to establish three mutually exclusive accelerometer-determined OA groupings: high OA, intermediate OA, and low OA.ResultsAccording to their summary score, ‘farm and nursery workers’ were classified as high OA and ‘secretaries, stenographers, and typists’ were classified as low OA. Consistent with previous research, some low OA occupational categories (e.g., ‘engineers, architects, and scientists’, ‘technicians and related support occupations’, ‘management related occupations’, ‘executives, administrators, and managers’, ‘protective services’, and ‘writers, artists, entertainers, and athletes’) associated with higher education and income had relatively greater amounts of MVPA compared to other low OA occupational categories, likely due to the greater percentage of men in those occupations and/or the influence of higher levels of leisure time PA. Men had more TAC, activity counts/minute and time in MVPA, but similar proportions of SB compared to women in all three OA groupings.ConclusionsObjectively measured PA allowed for a more precise estimate of the amount of PA and SB associated with different occupations and facilitated systematic classification of the 40 different occupational categories into three distinct OA groupings. This information provides new opportunities to explore the relationship between OA and health outcomes.