Validation of Youth Physical Activity Questionnaire using ActiGraph Accelerometer among Preadolescents and Adolescents in Urban Settings of Karachi, Pakistan

Background and Purpose Physical activity (PA) during childhood and adolescence is essential for good health, normal growth and development. Accurate measurement of PA in children has a great importance for assessing frequency, duration and intensity to examine the trends, dose response and effectiveness of interventions to reduce the attributable risk of chronic diseases later in life. Assessment of PA through objective methods is expensive and laborious to implement during surveys. Thus, estimates of PA rely on subjective instruments including the Youth Physical Activity Questionnaire (YPAQ). However, these instruments not been validated in the South Asian population. This study aiming to develop and validate a subjective tool that can accurately and precisely measure PA in children and youths to assess trends and effect of impending interventions to enhance PA in sedentary population.

Objectives The objectives of this study were to assess validity and reliability of an adapted version of YPAQ for various intensities of PA (sedentary to light and moderate to vigorous physical activities); and to determine ActiGraph optimal thresholds for various durations of moderate to vigorous physical activity (MVPA).

Methods PA measured for seven consecutive days through the gold standard ActiGraph GT3X accelerometer on 9 to 14 years aged school going children of both sexes in urban settings of Karachi. YPAQ was administered twice to estimate past week PA, first when Actigraph was attached and subsequently when it was retrieved. Height, weight, hip, waist circumference and blood pressure were measured on standard protocol. Spearman rank coefficients were calculated to assess the relationship between ActiGraph and YPAQ minutes reported in different domains and test-re-test reliability of repeat estimates of YPAQ one week apart. To test the hypothesis, the p values were calculated with the null hypothesized values of 0.3 and 0.6 for validity and reliability respectively. To assess degree of agreement between two measures, Bland Altman plots and to determine the threshold on YPAQ for the durations of MVPA, ROC curve were used. To process the accelerometer data Actilife software version 6; SPSS version 19 and Medcalc version 12 were used to perform all statistical analysis.

Results A total 252 children (52% boys) participated and 234 provided valid accelerometer data. Only 10% of children achieved recommended guidelines of 60 minutes of MVPA per day (boys 9% and girls 1%). From the total, proportion of sedentary activities was higher in girls than boys (48 vs. 39%); in contrary, for light and MVPA boys spent more time compare to girls (54 vs. 49%) and (6.2 vs. 2.7%) respectively; p value for all domains were <0.001. Spearmen coefficient for validity of total PA per week was 0.17 (p=0.035) and for MVPA 0.37 (p=0.259). Bland Altman plots showed an overestimation of total and MVPA and underestimation for sedentary and light domains by YPAQ. The sensitivity at 30 and 45 minutes of daily MVPA were 59.7 and 75% and specificity were 59.6 and 68.4%; the area under the curve were 0.68 and 0.65 respectively. Test re-test coefficients for overall and MVPA were 0.57 (p=0.403) and 0.617 (p=0.670) respectively.

Conclusions Validity and reliability of YPAQ is acceptable for MVPA, sensitivity and specificity was good to discriminate sedentary from non-sedentary population. YPAQ can be used at large scale to assess MVPA in children in urban communities in Pakistan, and possibly in South Asia. Children spent less time in MVPA particular older girls and suggest enhancing physical activity in severely sedentary groups for risk attenuation of chronic diseases in adulthood. School based interventions need to be revived for sustainable impact.

Support/Funding Source This work was supported by the Wellcome Trust UK, grant # [090680/Z/09/Z]