Characteristics of step-defined physical activity categories in U.S. adults..
OBJECTIVE
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).


METHODS
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.


METHODS
In-home interviews and physical examination components of NHANES.


METHODS
Overall, 4372 eligible adults wore accelerometers in the 2005-2006 NHANES; 628 were excluded, which yielded 3744 adults (of which 46.8% were men).


METHODS
Steps per day; body mass index (BMI); demographic, household and behavioral variables.


METHODS
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.
Pennington Biomedical Research Center, Baton Rouge, Louisiana, USA. susan-sisson@ouhsc.edu
Susan B
SB
Sisson
Sarah M
SM
Camhi
Catrine
C
Tudor-Locke
William D
WD
Johnson
Peter T
PT
Katzmarzyk
D000054:Acceleration; D000328:Adult; D000367:Age Factors; D016001:Confidence Intervals; D005260:Female; D015438:Health Behavior; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology; D016017:Odds Ratio; D057185:Sedentary Behavior; D014481:United States; D016138:Walking / Q000502:physiology*