Multi-level modelling of physical activity in nuclear families

Background: Few studies focus on the different dyadic relations among family members to study physical activity (PA) levels. Aim: The aim was to investigate predictors and sources of variance of PA levels in nuclear families using multi-level modelling. Subjects and methods: The sample consisted of 2661 Portuguese four-member nuclear families (10 644 subjects). PA was measured using a questionnaire and socioeconomic status (SES) was assessed by parental occupation. Height and weight were measured in children, while parents self-reported their values. Results: The results showed that intra-generational similarities were higher than inter-generational, with correlation values of 0.26 and 0.10, respectively. SES was unrelated to any family members' PA level. Being male (β = 0.26, t = 21.77), being older (β =-0.36, t =-4.73) and greater BMI for mothers (β = 0.02, t = 2.55) had effects on individuals' PA. Conclusion: These results suggest a strong dyadic resemblance in PA, showed different effects of gender, age and BMI on individuals' PA and demonstrated that multi-level modelling is a useful strategy to study PA in families.