While 24-h total sleep time (TST) is established as a critical driver of major depression, the relationship between sleep timing and regularity in relation to mental health remains poorly characterized. This is because most studies have relied on either self-report assessments or traditional objective sleep measurements restricted to cross-sectional time frames and small cohorts.
In this study, sleep with a wearable device, daily mood with a smartphone application and depression were studied in over 2 000 training physicians.
As a method, the 9-item Patient Health Questionnaire (PHQ-9) was implemented over the demanding first year of physician training (internship).
In 2115 interns, reduced TST (b = -0.11, p < 0.001), later bedtime (b = 0.068, p = 0.015), along with increased variability in TST (b = 0.4, p = 0.0012) and waking time (b = 0.081, p = 0.005) were associated with more depressive symptoms.
Overall, the aggregated impact of sleep variability parameters and mean sleep parameters on PHQ-9 were similar in magnitude (both r2 = 0.01). Within individuals, increased TST (b = 0.06, p < 0.001), later waking time (b = 0.09, p < 0.001), earlier bedtime (b = – 0.07, p < 0.001), as well as lower day-to-day shifts in TST (b = -0.011, p < 0.001) and waking time (b = -0.004, p < 0.001) were associated with improved mood the following day.
Variability in sleep parameters substantially impacted mood and depression, similar in magnitude to the mean levels of sleep parameters. Interventions that target sleep consistency, along with sleep duration, show promise in improving mental health.
Day-to-day variability in sleep parameters and depression risk: a prospective cohort study of training physician.
Day-to-day variability in sleep parameters and depression risk: a prospective cohort study of training physician. Yu Fang, Daniel B Forger, Elena Frank , Srijan Sen, Cathy Goldstein NPJ Digit Med. 2021 Feb 18;4(1):28. doi: 10.1038/s41746-021-00400-z.
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