Short, frequent physical activity breaks improve working memory while preserving cerebral blood flow in adolescents during prolonged sitting - AbbaH teen, a randomized crossover trial.

PURPOSE: Physical activity (PA) breaks during school lessons have been suggested as a promising strategy to improve working memory performance in children and adolescents. There is a lack of studies investigating the underlying physiological mechanisms of PA on cognition, especially among adolescents. This study aimed to investigate the effects of different types of short frequent PA on adolescents' cognitive task-related changes in cerebral blood flow in the prefrontal cortex (PFC) and working memory performance compared to prolonged sitting. METHODS: In this randomized crossover study, adolescents visited the laboratory on three different occasions for 80-minute sessions of prolonged sitting interrupted by four breaks for three minutes of simple resistance training (SRA), step-up at a pre-determined pace (STEP), or remaining seated (SOCIAL). Before and after each session, cognitive task-related changes in cerebral blood flow (oxygenated-hemoglobin, Oxy-Hb) during working memory tasks (1-, 2-, 3-back tests) were measured using functional near-infrared spectroscopy in the PFC. Accuracy and reaction time were derived from the working memory tasks. Linear mixed-effect models were used to analyze the data. RESULTS: A total of 17 students participated (mean age 13.6 years, 11 girls). Significant time x condition interactions were noted for Oxy-Hb in the most demanding working memory task (3-back), with a decrease following prolonged sitting in the SOCIAL condition compared to both the SRA (ß 0.18, 95% CI 0.12, 0.24) and the STEP (ß 0.11, 95% CI 0.05, 0.17). This was observed in parallel with improvements in reaction time following SRA (ß -30.11, 95% CI -59.08, -1.13) and STEP (ß -34.29, 95% CI -69.22, 0.63) although this was only significant for the SRA and no improvements in the SOCIAL condition. CONCLUSION: We found that short frequent PA breaks during prolonged sitting among adolescents can prevent the decrease in cognitive task-related changes in cerebral blood flow that occur following prolonged sitting. This was observed simultaneously with improvements in working memory, indicating that changes in cerebral blood flow could be one factor explaining the effects on working memory. Future studies should investigate the efficacy of implementing these PA breaks in schools. TRIAL REGISTRATION: Retrospectively registered on 21/09/2020, ClinicalTrial (NCT04552626).

Sick leave due to mental disorders, morbidity and mortality: a prospective study of discordant twin pairs.

PURPOSE: To investigate if sick leave due to mental disorders increases the risk of morbidity measured by inpatient and specialized outpatient care, and mortality among women and men, independent of familial factors. METHODS: An open cohort study of 4979 twin pairs discordant for sick leave due to mental disorders was conducted in 2005-2013. Twins were followed up in the cause of death and national patient registries until the end of study, emigration, death, and inpatient and specialized outpatient care. Conditional Cox proportional hazard regression, adjusting for the familial factors shared by the twins, was used to calculate hazard ratios (HR) with 95% confidence intervals (CI). In case of non-proportional hazards, time-varying covariates were used. RESULTS: Sick leave due to mental disorders increased the risk for inpatient care among men (HR: 1.90, CI 1.66-2.17) and women (HR: 1.39, CI 1.27-1.51). For men, the risk of outpatient care was higher the first 2 years (HR: 2.08, CI 1.87-2.31), after which it was attenuated (HR: 1.32, CI 1.02-1.70). For women, the HR was 1.57 (CI 1.47-1.68) for the whole study time. There was an increased risk of death among men (HR: 2.91, CI 1.70-4.99), but not among women (HR: 0.84, CI 0.53-1.35). CONCLUSIONS: Sick leave due to mental disorders was a risk factor for mortality for men only, and increased the risk of inpatient and specialized outpatient care among both women and men, but the risks were higher for men when stratifying for sex.