0181 Characterizing Sleep Regularity from Actigraphy in Younger and Older Adolescents

Abstract

Abstract Introduction Many adolescents experience variable sleep timing and restricted duration attributable to biopsychosocial influences. The Sleep Regularity Index (SRI) captures inter-daily stability of sleep/wake intervals as the likelihood of being asleep/awake at consistent times day-to-day. The SRI may capture unique dimensions of adolescent sleep given the ability to capture highly variable sleep/wake timing (including napping); however, SRI’s relative role in maturational sleep processes remains unknown. This study characterizes the SRI and sleep correlates (bedtime, midpoint, risetime, duration, and efficiency) in younger and older adolescents, including age-based comparisons. Methods Cross-sectional data were drawn from two cohorts: 30 younger (ages 9-10 years; 13 female; 24 White) and 38 older (ages 15-16 years; 20 female; 26 White) adolescents. Participants provided 7 consecutive nights (M=6.93±0.36) of sleep diaries and actigraphy on a self-selected sleep schedule while attending school. SRI was calculated as the probability of being asleep/wake at two points 24-hours apart (Philips et al., 2017), with higher scores demonstrating more regular sleep across days. Results SRI scores and distributions were similar between younger (M=79±9, range=58-94) and older (M=80±7, range=64-91) adolescents (t[66]=-0.58, p=.56). On average, younger adolescents reported a bedtime of 21:41±31, midpoint of 02:14±30, risetime of 06:47±36, and sleep duration of 9.11±0.52 hours. In contrast, older peers reported a later bedtime of 22:46±41 (t[66]=-7.21, p<.001) and midpoint of 02:47±29 (t[66]=-4.66, p<.001), with consistent risetime 06:49±29 (t[66]=-0.17, p=.87), and thus shorter sleep duration of 8.06±0.70 hours (t[66]=6.84, p<.001). In both cohorts, SRI was correlated with less wake-time after sleep onset (rs=-.93 to -.83, ps<.001) and greater sleep efficiency (rs=.80-.93, ps<.001), but not sleep duration or timing (ps=.18-.62). Conclusion This adolescent sample demonstrated greater sleep/wake regularity compared to previous reports of college students and adolescents/young adults, supporting the hypothesis that SRI may be a proxy for regularity of other aspects of daily living (e.g., fixed school start times). Adolescent SRI appears to be independent of sleep duration (consistent with previous findings) and timing, suggesting that SRI captures a distinct dimension of sleep. This research team plans to proceed with longitudinal analysis to clarify developmental trends, further explicating the potential informative role of SRI. Support (If Any) NIH R01 AA013252 and P20 GM139743.