Correlations of objective and self-report assessment of physical activity in twins: insights from the AUTBACK study.
Aim: To investigate the influence of genetic and environmental factors on physical activity levels. Methods: Data from 134 twins from Twins Research Australia, self-report and objective measures of physical activity were obtained by the International Physical Activity Questionnaire (IPAQ) (n = 110) and Actigraph (n = 120), respectively. Correlations were calculated for twin pairs stratified by zygosity (Monozygotic, MZ; Dizygotic, DZ) and using Spearman's correlation (rs) Results: Within-pair correlations were usually higher in MZ for the Actigraph (rs ranging from 0.34 [0.0 to 0.57] to 0.48 [0.22 to 0.68]) compared to IPAQ (rs ranging from -0.15 [-0.44 to 0.17] to 0.52 [0.25 to 0.72]. Correlations in DZ were lower for the Actigraph (rs ranging from -0.03 [-0.55 to 0.51] to 0.16 [-0.41 to 0.64]) compared to IPAQ (rs ranging from -0.11 [-0.59 to 0.43] to 0.50 [-0.01 to 0.81]). Correlations between Actigraph and IPAQ for all individuals were small for sedentary vs sitting time (rs = 0.28) and vigorous physical activity (rs = 0.27), but moderate for total physical activity (rs = 0.35). Conclusion: Within-family correlation of physical activity levels depends on the assessment, with less consistent results when its assessed by self-reported methods.