1099 Slow Wave Sleep Respiratory Rate Moderates Response to Morning Blue Light in Reducing Suicidal Cognitions

Abstract Introduction Respiratory rate and autonomic activity during sleep reflect sleep stage, with slow wave sleep being characterized by greater parasympathetic dominance and more rhythmic breathing. Both parasympathetic activity and respiratory rate have been linked with emotional state and emotion regulation. This study examined whether respiratory rate during slow wave sleep predicts changes in suicidal cognitions following morning blue light versus red placebo light. Methods Active-duty service members (N=37; ages 19-51; 21.6% women) with elevated depression completed a 6-week counterbalanced, crossover, placebo-controlled trial of active blue light (462nm) and red, or placebo light (661nm). Light was administered through AYO® eyewear for 30 minutes each morning over two 2-week periods with a 2-week washout. Participants wore a (Dreem3®) headband to assess sleep stage and respiratory rate. Respiratory rate during slow wave and REM sleep was examined a predictor of pre- to post-treatment change in suicidal cognition scores for both conditions (negative scores indicating improvement). Results Suicidal cognitions decreased more in the blue light condition than the placebo (blue M = -2.53, SD = 6.46; red M = -1.86, SD = 5.85; p = 0.087). Respiratory rates during sleep were also higher during blue light (blue M = 16.14, SD = 2.03; red M = 15.86, SD = 2.28; p = 0.057). Treatment condition moderated the influence of respiratory rate on suicidal cognition change. During blue light, higher respiratory rate during slow wave sleep predicted greater reductions in suicidal cognitions (Effect = -0.50, S.E. 0.25, p = 0.047); whereas, during placebo, higher respiratory rate predicted increases in suicidal cognitions (Effect = 0.34, S.E. 0.37, p = 0.021). Conclusion Respiratory rate during slow wave sleep is higher in the blue light condition and predicted larger decreases in suicidal cognitions across two weeks of morning exposure. In the placebo condition, however, higher respiratory rate during slow wave sleep predicted worsening suicidal cognitions. These findings suggest that early-morning blue light influences autonomic processes during deep sleep and may influence treatment response by supporting cognitive and emotion regulation pathways involved in reducing suicidal ideation. Support (if any) USAMRAA W81XWH2210990