Abstract
BackgroundThis study described the patterns of accelerometer-determined physical activity and sedentary behavior among adults using a nationally representative sample from the United States.MethodsUsing 2003-2006 National Health and Nutrition Examination Survey (NHANES) data, 7931 adults at least 18 years old wore an ActiGraph accelerometer for one week, providing at least 3 days of wear for >=8 hours/day. Cutpoints defined moderate to vigorous physical activity (MVPA; >= 2020 and >=760 counts/minute), vigorous physical activity (> = 5999 counts/minute), and sedentary behavior (<100 counts/minute). Latent class analysis (LCA) was used to estimate patterns of physical activity and sedentary behavior. All estimates were weighted to reflect the United States population.ResultsFor weighted percent of MVPA out of total wearing time, 5 classes were identified from least to most active: 65.3% of population (weighted mean 9.3 minutes/day), 24.9% (32.1 minutes/day), 3.2% that was low on the weekdays but much higher on the weekends (52.0 minutes/day), 5.9% (59.9 minutes/day), and 0.7% in the highest class (113.6 minutes/day). Using the lower MVPA threshold, 6 classes emerged with each class ranging in population from 1.2% to 43.6%. A vigorous activity class could not be derived due to low prevalence. For weighted percent of sedentary behavior out of total wearing time, 5 classes were identified from most to least sedentary: 6.3% of population (weighted mean 660.2 minutes/day), 25.1% (546.8 minutes/day), 37.7% (453.9 minutes/day), 24.0% (354.8 minutes/day), and 7.0% (256.3 minutes/day). Four of the classes showed generally similar results across every day of the week, with the absolute percents differing across classes. In contrast, the least sedentary class showing a marked rise in percent of time spent in sedentary behavior on the weekend (weighted mean 336.7-346.5 minutes/day) compared to weekdays (weighted mean 255.2-292.4 minutes/day).ConclusionThe LCA models provided a data reduction process to identify patterns using minute-by-minute accelerometry data in order to explore meaningful contrasts. The models supported 5 or 6 distinct patterns for MVPA and sedentary behavior. These physical activity and sedentary behavior patterns can be used as intervention targets and as independent or dependent variables in future studies of correlates, determinants, or outcomes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12966-015-0183-7) contains supplementary material, which is available to authorized users.
Highlights
In 2008, the United States government released its first physical activity recommendations [1] about the types and amounts of physical activity recommended to offer substantial health benefits to all Americans
We found that wearing time did not affect the classification of moderate to vigorous physical activity (MVPA) very much, the MVPA time as a percent of wearing time was the best representation of this variable, since it accounted for total wearing time per day and most efficiently separated unique latent classes
Hispanics have often self-reported low levels of MVPA relative to Non-Hispanic Whites when asked about leisure-time physical activity [13] or walking [14], our analyses indicated that Hispanics comprised a relatively larger proportion of the more active classes
Summary
In 2008, the United States government released its first physical activity recommendations [1] about the types and amounts of physical activity recommended to offer substantial health benefits to all Americans. The guidelines were based, in part, on epidemiologic studies of health outcomes, including all-cause and cardiovascular disease mortality. Those studies relied almost exclusively on selfreported physical activity. Self-reported measures, such as questionnaires, have a limited ability to detect physical activity that is routine and interspersed throughout the day, such as unstructured activities. These tend to be activities that are light or sedentary.
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