Objective: Adolescence is often associated with decline in physical activity (PA) and a circadian shift towards eveningness, but it is not known whether these transitions are intertwined. We explored longitudinally and in cross-section how chronotype and genetic liability for morningness associate with PA as self-reported and measured by actigraphy in early and late adolescence. Methods: Our sample comes from a longitudinal Finnish community-cohort born in 1998 with information on actigraph-based PA and objectively measured sleep-wake rhythm based on midpoint of sleep at ages 12 (N = 353, girls = 187) and 17 (N = 171, girls = 98). Information on self-reported circadian preference and subjective PA was available at age 17. The summarized genetic effects of multiple single nucleotide polymorphism for morningness was assessed by calculating polygenic score (PGS) based on the results on a recent genome-wide association study (GWAS). Results: PA declined by 40% (p = 0.36). However, those with circadian preference more towards eveningness at age 17 had more sedentary behavior (p <0.01) and a lower level of general (p = 0.01), light (p <0.01) and moderate to vigorous PA (p <0.05). They also had poorer subjective assessment of their fitness level (p <0.01) and they exercised less (all p = 0.13). Conclusions: Findings of this study highlighted the influence of circadian preference on physical activity behavior in adolescence. Self-assessed circadian preference towards eveningness associated with lower PA and greater decline of it during adolescence. Furthermore, PA declined significantly especially among boys from early to late adolescence. Interventions encouraging physical activity should target specifically evening-oriented adolescents. (C) 2020 Elsevier B.V. All rights reserved.Peer reviewe
