Public health surveillance of habitual physical activity in adolescents and adults in Namibia: a cross-sectional validation of activity questionnaires against accelerometry.

Abstract

Monitoring population-level physical activity is crucial for examining adherence to global guidelines and addressing obesity. This study validated self-reported moderate-to-vigorous physical activity (MVPA) against an accurate device-based method in Namibia. Adolescent girls (n = 52, mean age 16.2 years [SD 1.6]) and adult women (n = 51, mean age 31.3 years [SD 4.7]) completed the PACE+/GPAQ self-report questionnaires and were asked to wear an Actigraph accelerometer for 7 days. Validity of self-reported MVPA was assessed using rank-order correlations between self-report and accelerometry, and classification ability of the questionnaires with Mann-Whitney tests, kappa's, sensitivity and specificity. In the adolescents, Spearman's rank coefficients between self-reported MVPA (days/week) and accelerometry measured MVPA were positive but not significant (r=0.240; P=0.104). In the adults, self-reported MVPA (minutes/day) was moderately and significantly correlated with accelerometer-measured MVPA (r=0.396; P=0.008). In both groups, there was fair agreement between accelerometry and questionnaire-defined tertiles of MVPA (adolescents κ=0.267; P=0.010; adults κ=0.284; P=0.008), and measured MVPA was significantly higher in the individuals self-reporting higher MVPA than those reporting lower MVPA. The PACE+ and GPAQ questionnaires have a degree of validity in adolescent girls and adult females in Namibia, though more suitable for population than individual level measurement.