title: Validation of the Spanish version of the physical activity questionnaire used in the Nurses' Health Study and the Health Professionals' Follow-up Study.
abstract: OBJECTIVE
  The objective of this analysis was to test the validity of the estimates of energy expenditure and sedentary lifestyle obtained through a self-administered questionnaire of physical activity for Spanish-speaking people adapted from US questionnaires (Nurses' Health Study and Health Professionals' Follow-up Study) using a triaxial accelerometer (RT3 Triaxial Research Tracker) as the reference.
  
  
  METHODS
  Validation study, calculating the non-parametric correlation coefficients between the level of physical activity and sedentary lifestyle collected by the self-administered questionnaire and the triaxial accelerometer measurements. Percentage of misclassification and kappa coefficients were also calculated.
  
  
  METHODS
  The study population consisted of a sample of 40 obese women who were participants of the SUN (Seguimiento Universidad de Navarra) project (a prospective cohort study among Spanish university alumni). They were selected because of their peculiar metabolic characteristics, in the search for a sub-optimal scenario for validity.
  
  
  RESULTS
  Physical activity during leisure time (estimated as MET-h week(-1)) derived from the self-administered questionnaire moderately correlated with kcal day(-1) assessed through the accelerometer (Spearman's rho = 0.507, 95% confidence interval (CI) 0.232, 0.707). The Spearman correlation between the ratio of sedentary lifestyle to physical activity obtained through the questionnaire and the direct estimation (RT3) was -0.578 (95% CI -0.754, -0.325). The kappa index was 0.25 (P = 0.002) when assessing the cross-classification into quintiles and 0.41 for the dichotomous estimation of a sedentary lifestyle. Only 2.5% of participants were misclassified by the questionnaire more than two quintiles apart from the estimates of the RT3.
  
  
  CONCLUSIONS
  The moderate values obtained for correlation in a sub-optimal scenario for validity and the low percentage of extreme misclassification suggest the validity of the questionnaire to assess physical activity in Spanish-speaking women aged 20-50 years.
authors.affiliation: Department of Epidemiology and Public Health, University of Navarra, Irunlarrea s/n, E-31080 Pamplona, Spain. mamartinez@unav.es
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Martínez-González
authors.forename: Constanza
authors.initials: C
authors.lastname: López-Fontana
authors.forename: José Javier
authors.initials: JJ
authors.lastname: Varo
authors.forename: Almudena
authors.initials: A
authors.lastname: Sánchez-Villegas
authors.forename: J Alfredo
authors.initials: JA
authors.lastname: Martinez
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007899:Leisure Activities; D008019:Life Style; D008875:Middle Aged; D010809:Physical Fitness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013030:Spain; D011795:Surveys and Questionnaires / Q000592:standards*