PURPOSE: Evidence of shared physical activity (PA) habits within families is inconsistent. The present study aimed at examining intra-family resemblance in PA during different time segments of the week.
METHOD: This cross-sectional study used data from the Danish household-based population study Lolland-Falster Health Study. We assessed time spent in various PA intensities and behaviours using a dual-accelerometer system (Axivity AX3). At least one parent and one child per household provided data for a minimum of three weekdays and one weekend day. We analysed three time segments: early weekdays, late weekdays, and weekends. A linear mixed model regression analysis was used to estimate intraclass correlation coefficients (ICCs) of the total family, parent-child dyads, siblings, and parent-parent dyads for PA outcomes, adjusting for sex, age, parental education, and the interaction between sex and age.
RESULTS: We included 774 parents (57.9% female, 42.8±7 years) and 802 children (54.2% girls, 11.1±4.3 years) nested within 523 families. The clustering among the total family was stronger during late weekdays (ICCs 0.11-0.31) and weekends (ICCs 0.14-0.29) than during early weekdays (ICCs 0.02-0.19). We found stronger clustering among siblings (ICCs 0.08-0.47) and between parents (ICCs 0.02-0.52) than between parents and children (ICCs <0.01-0.37). Generally, the clustering was strongest for light PA, and among PA behaviours, walking showed the highest resemblance across all subgroups.
CONCLUSION: Initiatives to promote children's PA that involve parent or sibling co-participation may focus on the time segment and activity types with the highest resemblance. For the family as a whole, promoting walking or limiting sedentary activities may be a potential target for interventions during late weekdays and weekends.Trial registrationClinicaltrials.gov (NCT02482896).