Physical activity and hypothalamic-pituitary-adrenocortical axis function in adolescents

Little is known about the associations between physical activity (PA) and hypothalamic-pituitary-adrenocortical axis (HPAA) activity in adolescents. This knowledge could offer insight into the links between PA and well-being in youth. We studied whether objectively-measured PA is associated with diurnal salivary cortisol responses and morning salivary cortisol responses after a low-dose overnight dexamethasone suppression test (DST) in adolescent girls and boys. We conducted a cross-sectional birth cohort study in Helsinki, Finland. At a mean age of 12.4 (SD = 0.5) years, 150 girls and 133 boys wore wrist-worn accelerometers over at least 4 days to measure PA. Their salivary cortisol was measured across 1 day and upon awakening after a low-dose overnight DST (3 μg/kg of weight). Girls with higher overall PA and vigorous PA (VPA), and less sedentary time had lower salivary cortisol upon awakening and/or after (decreases between |0.17| and |0.25| SDs per SD increase in overall PA, VPA and decrease in sedentary time; P-values < 0.039). Boys with higher overall PA, and less sedentary time had greater suppression of salivary cortisol following overnight DST (suppression between |0.24| and |0.27| SDs per SD increase in overall PA and decrease in sedentary time; P-values < 0.012). Overall PA, VPA and sedentary time did not associate with DST suppression in girls or with diurnal salivary cortisol in boys. These results show that PA is associated with altered HPAA function in early adolescents, and that the associations are sex specific.