LAUSR

BACKGROUND Previous studies show contradictory results regarding the bidirectional association between physical activity and nighttime sleep. The objective of the present study was to add knowledge to these possible relationships using autoregressive models. METHOD 214 adolescents (117 boys and 97 girls), with a mean age of 13.31 years agreed to participate. The study variables were measured with accelerometers for 7 full days over three consecutive years. The mlVAR package was used to compute estimates from multivariate vector autoregression models. RESULTS The 5-delay models showed a better fit. Autoregressive effects were observed in sleep onset, sleep offset and sedentary behavior, which could explain the relationships found in previous studies between physical activity and sleep. Sleep onset, total sleep time, and sleep efficiency had direct effects on sedentary behavior. Moderate-to-vigorous physical activity was not related to any of the sleep variables. CONCLUSIONS The hypothesis that there are bidirectional/reciprocal relationships between physical activity and sleep cannot be accepted.