0166 Exposure to Blue-Enriched Light Following a 1-Hour Nap Extends Duration of Benefits to Sleepiness and Performance

Introduction When an unavoidable work task occurs during the night, workers must be sufficiently alert to perform safely. Both blue-enriched lighting and napping improve alertness and performance at night, but it is unclear how much or how long each intervention contributes to such improvements. We conducted a study to evaluate these interventions separately and together. Methods Participants completed two 26-hour laboratory visits, each following a week of 8.5 h time-in-bed (verified by actigraphy), where they completed an hourly 5-minute psychomotor vigilance task (PVT) and sleepiness visual analog scale. Participants were randomized by visit to undergo a control condition involving a 1-hour awake rest period under 150 lux lighting (rest+150) and one of three experimental conditions involving either 1) a 1-hour nap opportunity followed by 150 lux (nap+150), 2) a 1-hour nap opportunity followed by 250 melanopic EDI (mEDI; nap+250), or 3) a 1-hour rest period followed by 250 mEDI (rest+250). Each intervention began 20 hours after habitual waketime and the lights remained on post-nap/rest until discharge 7 hours later. We compared outcomes on the seven tests following the nap/rest between conditions using linear mixed-effects models with participant as a random effect, and age and sex as covariates, and performed post-hoc comparisons of each post-nap/rest test bout relative to the test immediately before the nap/rest. Results Thirty-two participants completed the study (16 female; MAge ± SD = 24 ± 5 years). Compared to control, participants rated their sleepiness as lower following a nap (nap+250 β=-14.3,p< 0.001; nap+150 β=-15.4,p< 0.001) and had faster PVT speeds (nap+250 β=0.21,p< 0.001; nap+150 β=0.23,p< 0.001), but there was no improvement in the rest+250 condition. Post-hoc analyses comparing each post-nap/rest test to the pre-intervention test revealed significantly lower sleepiness ratings 2-5 hours after a nap+250 (compared to control) and faster PVT speed at each hour (1-7) after nap/rest end. PVT speed was also better than control 1-4 hours after wake in the nap+150 condition. The rest+250 condition was not different. Conclusion Our preliminary results suggest that a short nap at night improves subsequent reaction time, while blue-enriched light sustains these effects. Support (if any) This study was funded by the NASA Human Research Program.