Relative Age Effect On Adolescent’S Physical Activity <And > Screen Time: A Cross-sectional Study In Japan

Relative age effect (RAE) is a phenomenon among the same grade, in which birth month makes a difference regarding physique, physical fitness, <and > sports skills. RAE of physique likely disappears in high school students, whereas there remains RAE of opportunities to continue sports activities until adulthood. However, no study targeting adolescents has clarified the stage that RAE of adolescent’s physical activity is notably seen. Although screen time is often regarded as the opposition of physical activity, it is unclear whether RAE of screen time exists, contrasting to physical activity. PURPOSE: We investigated RAE of adolescent’s physical activity <and > screen time. METHODS: We conducted a questionnaire survey regarding physical activity <and > screen time. In this study, 18,281 adolescents (10,299 men <and > 7,982 women, 10-18 years, 76 schools) were included. We specified adolescent’s birth month based on the questionnaire. We used the international physical activity questionnaire for Japanese early adolescents (IPAQ-JEA) <and > calculated adolescent’s daily moderate to vigorous intensity physical activity (MVPA) time. We also asked daily screen time, including television viewing, videogames, <and > internet use. We used multilevel linear regression analysis by sex <and > school stage (elementary school student, secondary school student, <and > high school student). RESULTS: Relatively younger men were significantly less likely to have MVPA time among secondary (b = -1.15, β = -0.06, p < 0.01) <and > high school students (b = -1.00, β = -0.04, p < 0.01), whereas relatively younger men spent more screen time only for high school students (b = 2.48, β = 0.04, p < 0.01). Contrastingly, RAE of neither physical activity nor screen time was observed for women. CONCLUSIONS: RAE of adolescent’s physical activity was observed in male secondary school <and > high school students, whereas RAE of screen time was noted in male high school students. These results suggest that RAE of physical activity can emerge since they are secondary school students, <and > the relatively younger men can replace physical activity with screen time. The authors declare no competing interests. This work was supported by JSPS KAKENHI Grant Number JP 18H01000, JSPS KAKENHI Grant Number JP 19 K21797, and JSPS KAKENHI Grant Number JP 21H00848.