Is sleep time associated with handgrip strength in adolescents from the 1997/1998 São Luís Birth Cohort?

This article aims to analyze the association between sleep time and handgrip strength in adolescents belonging to the 1997/1998 São Luís Birth Cohort. This was a cross-sectional study nested in a birth cohort study. One thousand two hundred sixty-nine individuals (18 and 19 years) wore an Actigraph® GTX3+ accelerometer on their wrist 24 hr/day for 7 consecutive days. Handgrip strength was measured using a digital hand dynamometer. We used directed acyclic graphs (DAG) to identify confounding variables. This sample of adolescents was mostly composed of men, with brown skin color, economic class C, which did not work, did not consume alcohol, did not smoke, and never used drugs. The mean value of handgrip strength was 28.2 (±9.3) kgf, and the mean of sleep time was 6 (±1.0) hours per day. The crude analysis showed an association between sleep time and muscle strength. An increase of one hour of sleep reduced the handgrip strength by 1.95 kgf (95%CI:-2.51;-1.39). However, after adjustment for confounders, the association was not maintained (β:-0.07; 95%CI:-0.48;0.36). Sleep time is not associated with handgrip strength in adolescents in São Luís.