Patterns of sedentary behavior, physical activity and cognitive outcomes in university young adultsrelationships with academic achievement and working memory capacity

Resumen

Introduction. The physical health benefits of sitting less and being more active are well documented. However, little is known about how sedentary behavior patterns, alone or in combination with physical activity, influence cognitive outcomes. In young university adults (i.e. 18-25 years old) an age group characterized by optimal cognitive functioning where academic achievement and cognitive control abilities are essential, research is even scarcer. In this context, this PhD thesis investigated the influence of sedentary behavior and physical activity on cognitive outcomes (working memory and academic achievement) in a sample of young university students. Methods. Three different studies were conducted. Study 1 validated a short working memory task that was subsequently used in studies 2 and 3. In study 1 (n=325) validity evidence was evaluated by comparing participants’ scores on the three shortened complex span tasks (Operation, Symmetry and Rotation Span) with two measures of reasoning ability (Raven’s Advanced Progressive Matrices and Number Series) and using confirmatory factor analysis. In addition, Cronbach’s coefficient alpha was computed for each complex span task as an index of internal consistency. Study 2 (n=371) and Study 3 (n=132) used cross-sectional designs to examine associations between sedentary behavior and physical activity patterns with working memory capacity and academic achievement. In both studies, academic performance was measured via grade point average and working memory capacity was assessed through the validated shortened complex span task. For physical activity and sedentary behavior variables, Study 2 assessed physical activity intensities (min/week of light, moderate and vigorous PA) and min/day of domain-specific sedentary behavior via self-report (International Physical Activity Questionnaire and Last 7 days sedentary behavior questionnaire). Study 3 employed objective assessments (activPALTM) to determine sedentary behavior variables (total sitting/lying time, total number of breaks in sitting/lying time and sedentary bouts duration), standing time, and physical activity variables (light and moderate-to-vigorous intensity physical activity). Pearson correlations determined which variables were included in the analysis, and separate multiple linear regression models were performed to examine combined associations between sedentary behavior and physical activity variables with cognitive outcomes. Results. Study 1 indicated that the short version of the Spanish complex span has satisfying psychometric qualities for assessing working memory capacity in Spanish-speaking university students. Study 2 found that performing more than 3h/week of moderate physical activity was related to increases in working memory capacity, but physical activity intensities were not associated with academic performance. Spending >3h/day seated on weekends while performing non-screen leisure activities was related to reduced working memory capacity, after adjusting for physical activity, while spending >3 h/weekday seated in these sedentary activities or in leisureforms of screen time were inversely associated with academic performance regardless of physical activity level. Study 3 indicated that, independently of physical activity, the amount of time spent in sedentary bouts of 10-20min during weekdays was positively related to academic achievement while sedentary bouts of 20-30min during weekend days were negatively related to working memory capacity. No significant associations were identified for total sitting time. Conclusions. Time spent in specific leisure domains of sitting time may detract from academic performance and working memory capacity, independently of physical activity intensity and duration. In addition, preliminary results indicated that breaking prolonged sitting time may differentially impact distinct cognitive outcomes by optimizing cognitive operations associated with academic performance and impairing working memory processes.