Purpose: Descriptive physical activity epidemiology of the U.S. population is critical for program development and resource allocation. The purpose of this project was to describe step-defined categories (as measured by accelerometer) of U.S. adults and to determine predictors of sedentary classification (<5000 steps/d).
Design: The National Health and Nutrition Examination Survey (NHANES) is an annual, nationally representative survey used to determine the health status of the U.S. populace.
Setting: In-home interviews and physical examination components of NHANES.
Participants: Overall, 4372 eligible adults wore accelerometers in the 2005-2006 NHANES; 628 were excluded, which yielded 3744 adults (of which 46.8% were men).
Measures: Steps per day; body mass index (BMI); demographic, household and behavioral variables.
Analysis: Means and frequencies were calculated. Logistic regression was utilized to determine predictors of sedentary classification.
Results: Overall, 36.1% were sedentary (i.e., <5000 steps/d); 47.6% were low to somewhat active (5000-9999 steps/d); 16.3% were active to highly active (≥10,000 steps/d). Advancing age (odds ratio [OR], 1.95; confidence intervals [CIs], 1.78, 2.13), higher BMI (OR, 1.40; CIs, 1.23, 1.59), female sex (OR, 1.86; CIs, 1.46, 2.36), African-American versus European-American ethnicity (OR, 1.36; CIs, 1.13, 1.65), household income versus ≥$45,000 (<$25,000: OR, 1.94; CIs, 1.40, 2.69; $25,000-$44,000: OR, 1.51; CIs, 1.23, 1.85), and current versus never smoker (OR, 1.53; CIs, 1.26, 1.86) variables had higher odds of sedentary classification. Usual daily occupational/domestic physical activity categories of standing/walking (OR, .51; CIs, .38, .69); lifting/climbing (OR, .26; CIs, .17, .38); and heavy loads/labor (OR, .16; CIs, .10, .26) had lower odds of sedentary classification than sitting.
Conclusions: Over one-third of the U.S. population was classified as sedentary by accelerometer-determined steps per day, and several characteristics predicted sedentary classification.