Effect Of Menstrual Cycle On Objectively-measured Sleep In Active, Eumenorrheic Females

PURPOSE: The menstrual cycle (MC) is associated with changes in self-reported sleep duration and quality. In particular, the mid-to-late luteal phase of the MC is associated with poor sleep quality due to increases in body temperature and onset of premenstrual symptoms. The purpose of this study was to investigate whether MC phase impacts objectively-measured sleep duration and quality in physically active, eumenorrheic females. METHODS: Seven eumenorrheic females (Age: 34 ± 6 y, VO2max: 37.5 ± 3.8 ml/kg/min) wore a Fitbit Inspire 3 fitness and sleep tracker on their wrist for 2 - 5 months to objectively measure sleep duration and sleep quality. MC phase was determined using calendar-based counting, ovulation test strips, and serum hormone profile. Follicular phase was defined as the start of menstruation up to ovulation. Mid-to-late luteal phase was defined as 7 days after ovulation through end of cycle. The Fitbit measured sleep duration and indices of sleep quality namely, awake time, and light and deep sleep. In addition, we calculated sleep efficiency (%) by dividing sleep duration by time spent in bed. A minimum of 5 nights of sleep during each phase of MC was required for analyses. A one-way, repeated measures ANOVA was used to assess differences in sleep duration and quality across MC. RESULTS: Sleep duration was higher during follicular (426 ± 44 min) compared to mid-to-late luteal phase (408 ± 45 min) (F[1,6] = 2.06, p = 0.20; effect size = 0.26). However, after accounting for time in bed, sleep efficiency did not differ by MC phase (follicular: 88.3 ± 1.7 %, mid-to-late luteal: 87.7 ± 1.9 %; p = 0.30). Light sleep was higher in follicular (272 ± 19 min) compared to mid-to-late luteal phase (245 ± 19 min) (F[1,6] = 6.82, p = 0.04; effect size = 0.53). In contrast, deep sleep was higher in mid-to-late luteal (77 ± 13 min) than follicular phase (67 ± 15 min) (F[1,6] = 5.23, p = 0.06; effect size = 0.47). CONCLUSIONS: These preliminary results in 7 eumenorrheic females suggest that sleep duration is slightly longer (18 min) in the follicular phase. However, sleep efficiency was not different between MC phases. Furthermore, sleep quality was better in the mid-to-late luteal phase as evidenced by less light sleep, and more deep sleep. These findings should be viewed as preliminary and need to be confirmed with polysomnography. Texas Woman's University ORSP Small Grant