| Summary: | 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.
Design and setting: 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.
Subjects: 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 week21) derived
from the self-administered questionnaire moderately correlated with kcal day21
assessed through the accelerometer (Spearman’s r ¼ 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 20.578 (95% CI 20.754, 20.325). The kappa index was 0.25 (P ¼ 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.
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