Association of change in physical activity associated with change in sleep complaints: results from a six-year longitudinal study with Swedish health care workers.

Objective: To increase our understanding of patterns of change in physical activity and sleep complaints and to test whether intra-individual changes in physical activity are correlated with intra-individual changes in sleep complaints across four measurement time-points over six years, adopting both a between-person and within-person perspective.

Methods: Data from a longitudinal cohort study were used in this research. At baseline, 3187 participants took part in the study (86% women, M = 46.9 years). The response rate was 84% (n = 3136) after two years, 60% (n = 2232) after four years, and 40% (n = 1498) after six years. Physical activity was assessed with the [51] widely used 4-level physical activity scale (SGPALS), and sleep complaints with three items from the Karolinska Sleep Questionnaire (KSQ). Patterns and correlations of change between physical activity and sleep complaints were examined with latent growth curve modeling.

Results: Changes in physical activity were associated with changes in sleep complaints across the six years. More specifically, significant associations occurred between baseline levels, correlated (between-person) change, and coupled (within-person change). These associations indicate that higher physical activity levels are not only cross-sectionally linked with fewer sleep complaints, but that increases in physical activity over time (either in comparison to others or to oneself) are paralleled by decreases in sleep complaints.

Conclusions: Given that changes in physical activity and sleep are correlated, our findings indicate that it is worthwhile to initiate more physically active lifestyles in physically inactive individuals; and to ensure that those who are already physically active maintain their physical activity levels over longer periods.