Physical Activity and Chronic Stress in Early Life: Findings From the 2015 Pelotas (Brazil) Birth Cohort

Background : The association of physical activity through early childhood on children’s chronic stress still is unclear. Therefore, the aim of the present study is to test the association of physical activity through early childhood (1–4 y) with chronic stress, measured by hair cortisol at age 4. Methods : Longitudinal study including children from the 2015 Pelotas (Brazil) Birth Cohort. Cortisol at age 4 was measured using a hair sample, which provided cortisol concentration from the past months. Physical activity was measured using accelerometers at 1, 2, and 4 years. Linear regression models were used to assess the association between physical activity and chronic stress. Trajectory models were also applied to examine chronic stress in relation to physical activity patterns throughout early childhood. Results : Children with valid physical activity and hair cortisol data were included in the analyses (N = 1475). Three groups of physical activity trajectories between 1 and 4 years were identified: low, medium, and high. No association between physical activity at 1, 2, and 4 years and chronic stress at age 4 was observed. However, children in the “high” physical activity trajectory presented low cortisol concentration; the magnitude of the regression coefficient was slightly larger in girls ( β = −0.125; 95% confidence interval, −0.326 to 0.074) than boys ( β = −0.051; 95% confidence interval, −0.196 to 0.09). Conclusion : There was no clear association between physical activity and chronic stress in early childhood. Trajectories models suggest that higher activity throughout early childhood may positively impact chronic stress; however, more studies are needed to confirm that hypothesis.