Day-to-day variations in health behaviors and daily functioning: two intensive longitudinal studies

Abstract

Health behaviors tend to show a high variability over time within the same person. However, most existing between-person research can only assess a snapshot of a person’s behavior. Two longitudinal studies examine the natural daily variability in health behaviors and their implications for affect and academic performance. In two intensive longitudinal studies with up to 65 assessment-days over one academic year, university students (Study 1: N = 292; Study 2: N = 304) reported sleep quality, physical activity, snacking, learning goal achievement, positive and negative affect. Multilevel structural equation models showed that on days on which participants reported better sleep quality or more physical activity than usual, they also reported increased positive affect, decreased negative affect, and better learning goal achievement. Higher snacking was only associated with increased positive affect. Affect was a mechanism underlying the relation between health behaviors and learning goal achievement. Importantly, sleep quality was a stronger predictor for affect and learning goal achievement than physical activity or snacking. These findings have important implications for low-threshold interventions targeting the improvement of daily functioning.