Actigraphy-defined measures of sleep and movement across the menstrual cycle in midlife menstruating women: Study of Women's Health Across the Nation Sleep Study.

OBJECTIVE: This study aims to evaluate patterns in actigraphy-defined sleep measures across the menstrual cycle by testing the hypothesis that sleep would be more disrupted in the premenstrual period (ie, within the 14 d before menses).
METHODS: A community-based longitudinal study of wrist actigraphy-derived sleep measures was conducted in 163 (58 African American, 78 white, and 27 Chinese) late-reproductive-age (mean [SD], 51.5 [2.0] y) women from the Study of Women's Health Across the Nation Sleep Study. Daily measures of sleep (sleep efficiency [%] and total sleep time [minutes]) and movement during sleep (mean activity score [counts]) were characterized using wrist actigraphy across a menstrual cycle or 35 days, whichever was shorter. Data were standardized to 28 days to account for unequal cycle lengths and divided into four weekly segments for analyses.
RESULTS: Sleep efficiency declined gradually across the menstrual cycle, but the decline became pronounced on the fourth week (the premenstrual period). Compared with the third week, sleep efficiency declined by 5% (P < 0.0001) and mean total sleep time was 25 minutes less (P = 0.0002) on the fourth week. We found no significant differences between the mean for the second week and the mean for the third week. The association of weekly segments with sleep efficiency or total sleep time was modified by sociodemographic and lifestyle factors, including body mass index, race, study site, financial strain, marital status, and smoking.
CONCLUSIONS: Among late-reproductive-age women, sleep varies systematically across the menstrual cycle, including a gradual decline in sleep efficiency across all weeks, with a more marked change premenstrually during the last week of the menstrual cycle. These sleep changes may be modified by altering lifestyle factors.