The effect of physical activity timing on insomnia and sleep quality: a randomized cross-over trial in older adults

Insomnia symptoms are common in older adults. While observational studies suggest physical activity (PA) timing affects health outcomes, its effect on sleep remains unclear. We compared morning versus evening PA effects on insomnia severity and sleep quality in older adults with insomnia symptoms.

Eligible participants were aged 60-80 years with (sub)clinical insomnia (Insomnia Severity Index [ISI] score ≥10). In a randomized cross-over trial, participants engaged in coached PA in the morning (10:00-11:00) or evening (19:30-20:30) for 14 days each. ISI scores were assessed post-intervention. Objective sleep parameters-duration, latency, efficiency, and timing-were assessed with a Withings Sleep Analyzer under the mattress. Subjective sleep quality was reported daily via smartphone app. Salivary dim light melatonin onset (DLMO) was measured on the final day of each intervention.

Sleep data was available from 31 participants (mean age 69.8 years ± 5; 64.5% women). Although ISI improved after all intervention periods compared to baseline (estimated marginal mean ISI baseline: 14.44 points, inactive period: 12.37 points, active morning: 11.87 points, active evening: 12.35 points), there was no evidence for a difference in ISI between the active evening and active morning period (β 0.55, 95%CI -0.80, 1.91). compared to the active evening period, sleep midpoint occurred earlier during the active morning period (4:13 vs. 3:54 a.m. respectively, β 0.31 min, 95%CI 0.14, 0.48). No differences were observed in subjective sleep quality or DLMO.

While morning vs. evening PA timing did not impact most sleep quality measures, it influenced sleep timing. Larger studies are needed to define optimal and personalized PA timing for improving sleep.