Reliability and validity of the Youth Leisure-time Sedentary Behavior Questionnaire (YLSBQ).

Objectives: To develop a questionnaire able to assess time spent by youth in a wide range of leisure-time sedentary behaviors (SB) and evaluate its test-retest reliability and criterion validity.
Design: Cross-sectional observational.
Methods: The reliability sample included 194 youth, aged 10-18 years, who completed the questionnaire twice, separated by one-week interval. The validity study comprised 1207 participants aged 8-18 years. Participants wore an accelerometer for 7 consecutive days. The questionnaire was designed to assess the amount of time spent in twelve different SB during weekdays and weekends, separately. In order to avoid usual phenomenon of time over reporting, values were adjusted to real available leisure-time (LT) for each participant. Reliability was assessed by using Intraclass Correlation Coefficients (ICC) and weighted (quadratic) kappa (k), and validity was assessed by using Pearson correlation and Bland-Altman plots.
Results: The reliability of questionnaire showed a moderate-to-substantial agreement for the most (91%) of items (k=0.43-0.74; ICC=0.41-0.79) with three items (4%) reaching an almost perfect agreement (ICC=0.82-0.83). Only 'sitting and talking' evidenced fair-to-moderate reliability (k=0.27-0.39; ICC=0.34-0.46). The relationship between average sedentary time assessed by the questionnaire and accelerometry was moderate (r=0.36; p<0.001). Systematic biases were not found between questionnaire and accelerometer sedentary time for average day (r=0.05; p=0.11) but Bland-Altman plots suggest moderate discrepancies between both methods of SB measurement (mean=19.86; limits of agreement=-280.04 to 319.76).
Conclusions: The questionnaire showed moderate to good test-retest reliability and a moderate level of validity for assessing SB in youth, similar or slightly better to previously published in this population.
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