Health-related quality of life in school-aged boys and girls: longitudinal associations with physical activity and sedentary behaviour in the HAPPY study

Health-related quality of life (HRQoL) is positively associated with physical activity (PA) and negatively associated with sedentary time (SED) assessed by self- and proxy-report in children. However, there is a dearth of longitudinal evidence using device-measured PA and SED in this population. This study aimed to examine longitudinal associations of device-measured PA and SED as well as parent-reported screen time with HRQoL in primary (elementary) school-aged boys and girls. Data from waves 2 and 3 (child ages 6–8 and 9-11y, respectively) of the Healthy Active Preschool and Primary Years (HAPPY) Study were analysed. At wave 2, children wore ActiGraph GT1M accelerometers to assess time in SED and light-, moderate- and vigorous-intensity PA (LPA, MPA and VPA). Parents reported their child’s usual screen time (television viewing, computer/internet use, computer/electronic games, handheld electronic games). At wave 3, parents reported their child’s HRQoL using the Pediatric Quality of Life Inventory. Mixed-effects linear models were used to assess longitudinal associations of different intensities of PA, SED, and screen time with HRQoL scores. Analyses were stratified by sex of the child and adjusted for child age, BMI z-score and maternal education, with child and preschool/childcare centre of recruitment as random-effects. Boys had less SED and more MPA, VPA, TPA, electronic game use, handheld electronic game use and total screen time than girls (all p < 0.05); there were no sex differences in LPA, television viewing, computer/internet use, or HRQoL scores. For boys, VPA predicted better physical HRQoL (beta β = 0.18, 95%CI 0.02, 0.35). For girls, using electronic games predicted lower psychosocial HRQoL (β=-0.09, 95%CI -0.16, -0.01), while handheld electronic games and total screen time predicted lower physical HRQoL (β=-0.19, 95%CI -0.33, -0.06, and β=-0.04, 95%CI -0.07, -0.004, respectively) and total HRQoL (β=-0.12, 95%CI -0.23, -0.01, and β=-0.03, 95%CI -0.05, -0.001, respectively). Higher VPA predicted better physical HRQoL for boys; since boys were more active than girls, girls may not have engaged in sufficient VPA to benefit their HRQoL. Further research is needed to examine specific types of screen use, given the observed detrimental associations with HRQoL for girls.