Polar’s big data reveals an interesting interaction between sleep and evening physical activity
Professional and colloquial sleep hygiene guidelines often advise against evening physical activity, despite meta-analyses of laboratory studies concluding that evening exercise does not impair sleep. Now, a new collaborative study conducted by Polar Research Center, in collaboration with Flinders University and University of Helsinki, has investigated for the first time the association between objectively measured evening physical activity and sleep within a real-world big data sample.
To conduct this study, researchers analyzed a total of 153,154 nights from 12,638 individuals aged 18-60 years (M=40.1 SD=10.1; 44.5% female). Nighttime sleep and physical activity minutes were assessed using Polar wearable devices for 14 consecutive days. In 12.4% of the evenings, participants logged thirty minutes or more of moderate-to-near maximal physical activity during the three hours before sleep onset. Physical activity was more frequent on weekdays compared to weekends (13.3% vs 10.2% respectively, p < 0.001).
Linear mixed modelling revealed that sleep efficiency was not significantly associated with evening physical activity: sleep duration was 3.4 minutes longer on average on the nights in which participants engaged in 30 minutes or more of moderate-to-intense physical activity. Other sleep metrics showed a stronger correlation. For example, evening physical activity was linked to earlier sleep onset and offset times (–13.7 and –9.3 mins, respectively). Overall, these effects, however, were greater - but still very small - on weekdays compared to weekends.
The results of the present study provide further evidence for the lack of meaningful links between sleep duration or quality and physical activity in the hours preceding sleep. Taken together with recent meta-analytic findings, these findings suggest that changes in public health recommendations are warranted regarding evening physical activity and its relation to sleep.
Michal Kahn et al. Is It Time We Stop Discouraging Evening Physical Activity? New Real-World Evidence From 150,000 Nights. Front. Public Health, 04 November 2021 | https://doi.org/10.3389/fpubh.2021.772376