Rem Sleep Is The Dominant Sleep Stage In Mediating Mood State

PURPOSE: Previous research shows sleep (duration, onset, and wake time) is positively related to mood state, whereby decreased total sleep time (TST), increased sleep onset, and higher wake after sleep onset (WASO) lead to negative mood states. However, minimal research has explored how modifying the time spent in specific sleep stages affects mood state. Therefore, the purpose of this study was to evaluate how changes in TST and sleep stages (via a temperature-controlled mattress cover; TCM) affect mood state. METHODS: Twenty-two adults (16 M, 6 F; 38.2 ± 13.3 y) slept on a TCM for 6 nights: 4 with TCM on and 2 with TCM off. Subjects’ temperatures varied nightly when temperature was on. Subjects took the Brunel Profile of Mood State (BRUMS) each morning, which has 24 questions on a 5-point Likert scale, comprising 5 negative subscales (Tension, Depression, Fatigue, Confusion and Anger) and 1 positive subscale (Vigor). These subscales derived an overall mood score (lower score means better mood). Subjects reported daily sleep quality. The TCM recorded TST, WASO, rapid eye movement (REM), deep, and light sleep percentages. Correlations and multiple linear regressions were used to find relationships between mood scores and sleep metrics across all nights. RESULTS: Of the sleep stages, REM % was the most correlated sleep stage with the overall mood score (r = -0.31, P < 0.01), Confusion (r = -0.36; P < 0.001), and Anger (r = -0.33; P < 0.01). Light sleep above the typical range of 40-65% led to a decrease in REM %, which worsened mood (r = 0.29, P < 0.01). Deep sleep was not correlated to mood (r = -0.01; P = 0.92). Increased reported sleep quality was associated with improved overall mood (r = -0.44, P < 0.01) and decreased Fatigue (r = -0.42, P < 0.01). Lastly, TST (β = -2.3; P < 0.01) and WASO (β = 0.1; P < 0.01) were significant predictors of overall mood score (r2 = 0.30; P < 0.01). CONCLUSIONS: REM sleep was the most highly correlated sleep stage with mood compared to light and deep sleep stages. In particular, increased REM sleep corresponded with improved mood, particularly by decreasing Anger and Confusion.