title: Differences in physical activity prevalence and trends from 3 U.S. surveillance systems: NHIS, NHANES, and BRFSS.
abstract: BACKGROUND
  Three U.S. surveillance systems-National Health Interview Survey (NHIS), National Health and Nutrition Examination Survey (NHANES), and Behavioral Risk Factor Surveillance System (BRFSS)--estimate physical activity prevalence.
  
  
  METHODS
  Survey differences were examined qualitatively. Prevalence estimates by sex, age, and race/ethnicity were assessed for comparable survey periods. Trends were examined from NHIS 1998 to 2007, NHANES 1999 to 2006, and BRFSS 2001 to 2007.
  
  
  RESULTS
  Age-adjusted prevalence estimates appeared most similar for NHIS 2005 (physically active: 30.2%, inactive: 40.7%) and NHANES 2005 to 2006 (physically active: 33.5%, inactive: 32.4%). In BRFSS 2005, prevalence of being physically active was 48.3% and inactive was 13.9%. Across all systems, men were more likely to be active than women; non-Hispanic whites were most likely to be active; as age increased, overall prevalence of being active decreased. Prevalence of being active exhibited a significant increasing trend only in BRFSS 2001 to 2007 (P < .001), while prevalence of being inactive decreased significantly in NHANES 1999 to 2006 (P < .001) and BRFSS 2001 to 2007 (P < .001).
  
  
  CONCLUSIONS
  Different ways of assessing physical activity in surveillance systems result in different prevalence estimates. Before comparing estimates from different systems, all aspects of data collection and data analysis should be examined to determine if comparisons are appropriate.
authors.affiliation: Division of Nutrition, Physical Activity, and Obesity, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Carlson
authors.forename: Dianna
authors.initials: D
authors.lastname: Densmore
authors.forename: Janet E
authors.initials: JE
authors.lastname: Fulton
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Yore
authors.forename: Harold W
authors.initials: HW
authors.lastname: Kohl
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D040343:Behavioral Risk Factor Surveillance System; D005006:Ethnicity / Q000706:statistics & numerical data; D015444:Exercise; D005260:Female; D015438:Health Behavior / Q000208:ethnology; D006306:Health Surveys; D040361:Healthy People Programs; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D011594:Psychometrics; D017678:Sex Distribution; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology