0773 Influence of Chronotype and Time-of-Day on Objective Alertness

Abstract Introduction Chronotype describes individual variation in the preferred timing of the sleep-wake cycle and can influence when a person feels most alert. Misalignment between chronotype and timing of assessments of vigilance/alertness may affect performance. We evaluated these relationships using questionnaires and psychomotor vigilance test (PVT) data. Methods De-identified data from adults enrolled in the Stanford Technology Analytics and Genomics in Sleep (STAGES) study was obtained from the National Sleep Research Resource. Data included demographics, questionnaires, polysomnography (PSG), sleep diaries, and a 3-minute PVT. The PVT was performed one time per subject either the evening before or morning after the PSG. The time of PVT completion was categorized into intervals of 7-10am (n=182), 11am-7pm (n=366), or 8-11pm (n=581). Chronotype was determined based on responses to the reduced Morningness-Eveningness Questionnaire as evening-type (n=261), neither-type (n=578), or morning-type (n=290). Analysis of covariance was used to compare the number of 355 msec lapses (primary outcome) on PVT among each chronotype based on the time-of-day the PVT was completed, adjusted for age, sex, body mass index (BMI), apnea-hypopnea index (AHI), and sleep duration. Results 1129 patients (47% males) were included, with a mean (SD) age of 46.0 (15.1) years, BMI of 31.4 (8.8) kg/m2, and AHI of 13.8 (16.4) events/hour. In covariate-adjusted analyses, the number of lapses did not significantly differ based on time-of-day for the total cohort (p=0.28). However, when evaluating time-of-day effects separately by chronotype, there were significant differences in PVT performance. Morning-types had more lapses in the evening (8-11pm: 14.69 [12.63, 16.75] lapses) compared to the morning (7-10am: 7.79 [6.37, 9.21] lapses; p< 0.001). On the other hand, evening-types had more lapses in the morning (7-10am: 16.20 [10.87, 21.57] lapses) compared to the evening (8-11pm: 10.10 [8.77, 11.40] lapses; p=0.02). Time-of-day did not significantly impact PVT performance in subjects who were neither-type (p=0.33). Conclusion Evening-types have more PVT lapses in the morning reflecting their difficulties waking up. Morning-types have more lapses in the evening. These data emphasize the importance of considering the relationship between an individual’s chronotype and the time of assessment when interpreting vigilance/alertness as determined by PVT performance. Support (if any) NIH grant P01 HL160471 R21 HL172127