1257 Persistent Reduction in REM Sleep Following the Spring Daylight Saving Time Transition in a Large Real-World Cohort

Abstract Introduction The spring transition into Daylight Saving Time (DST) introduces an abrupt one-hour shift that may disrupt sleep beyond the first night. It remains unclear how sleep architecture changes during the weeks before and after this transition. Methods We examined 117,578 U.S. adult users (~2.67 million nights; 39.5% female; mean age=47±12.8 years) of a commercially available under-mattress device (Sleeptracker-AI Monitor, Fullpower Technologies Inc., California, USA). Sleep architecture data was gathered from two weeks prior to DST (2/22/25) to one week after (3/21/25), labeled weeks -2, -1, 0 (week of DST), and 1. To understand DST’s immediate impact, we compared sleep parameters on the Sunday DST began to the two previous Sundays using Welch’s t-tests. Next, after excluding weekends, we computed each participant’s mean weekly metrics for weeks -2 through +1 and compared them using Welch’s t-tests. Results In comparison to the previous two Sundays, the first night of DST exhibited shorter total sleep time (TST) (week 0 vs. -2: -13.7 min; week 0 vs. -1: -12.9 min) and lower REM% (week 0 vs. -2: -0.11%; week 0 vs. -1: -0.14%; p< 0.001 for all comparisons). However, TST returned close to pre-DST levels during week 0, remaining only slightly lower than in weeks -2 (week 0 vs. -2: -0.63 min) and -1 (week 0 vs. -1: -1.1 min; p< 0.01 for both comparisons). By week +1, TST no longer differed from weeks -2 or -1 (p>0.05). In contrast, REM% remained lower in both weeks 0 (week 0 vs. -2: -0.18%; week 0 vs. -1: -0.24%) and +1 (week +1 vs. -2: -0.06%; week +1 vs. -1: -0.12%) relative to pre-DST levels (p< 0.0001 for all comparisons). We didn't observe as significant changes in weekday deep sleep proportion following DST. Conclusion In a large real-world sample, we found that although both REM% and total sleep time (TST) decreased on the first night of DST, only TST returned to pre-DST levels in the subsequent weeks, whereas the reduction in REM% persisted. These findings may help explain ongoing sleep complaints following spring DST and underscore the value of at-home sleep technologies for understanding real-world sleep patterns. Support (if any) Fullpower Technologies.