Menstrual variations of sleep-wake rhythms in healthy women

Description

The ovarian steroid hormones estrogen and progesterone, which fluctuate dynamically with the estrous cycle, alter the circadian behavioral rhythms in mammals. However, it remains unclear whether the sleep-wake rhythm fluctuates with the menstrual cycle in humans. To determine the relationship between the menstrual cycle and sleep-wake rhythms, we evaluated the objective and long-term sleep-wake rhythms of ten healthy women using a recently developed wearable device. The results showed a strong negative correlation between the sleep midpoint and the Quasi Peak (QP) value (an indicator of rhythm robustness) and a positive correlation between the menstrual cycle (days) and social jet lag (hours). These results suggest that healthy women with late sleeping habits have a disturbed sleep-wake rhythm and that irregular habits prolong the menstrual cycle. The sleep midpoint and QP values showed variations during the menstrual cycle. The QP value in the follicular phase was significantly higher than those in the menstrual and luteal phases. In rodents, the phase of locomotor activity rhythm advances, and activity increases at night during proestrus. The increase in QP values during the follicular phase, when estrogen is relatively high, may be due to the increased activity caused by estrogen. These results suggest that ovarian steroid hormones influence sleep-wake rhythms in women. Although it is necessary to verify the results of this study under various conditions, it will be possible to accurately predict the day of ovulation using only the acquisition of sleep-wake rhythms with wearable devices.

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Procedures Before participating in the study, participants completed a self-administered questionnaire, the PSQI, and the MCTQ. The items of the self-administered questionnaire included age and regular medication. Before the intervention, participants received a smartwatch (Apple Watch Series 3, Apple, Cupertino, CA, USA), a clinical thermometer (TDK, Tokyo, Japan) for basal body temperature recording, and ovulation day prediction test drugs (Do-Test® LH II, Rohto Pharmaceutical, Osaka, Japan) for determining the day of ovulation. Basal body temperature The participants measured their basal body temperature every morning using the clinical thermometer. Sleep parameters (duration, midpoint, and QP value) The participants wore the smartwatch as much as possible during their daily activities, except when bathing, and the smartwatch was linked to a sleep-recording application (Auto Sleep, Tantsissa, Australia) to measure sleep duration and depth. The participants regularly checked and corrected the data in the application and adjusted it to be as accurate as possible. Non-nighttime sleep, such as naps, was also recorded and treated as one sleep section if there were no consecutive awakenings for 120 minutes. Sleep duration and sleep midpoint were defined as the interval between falling asleep and waking and the median of the time of falling asleep and waking time, respectively. The acquired sleep-wake data were expressed as a number from 0 to 5 every 15 minutes according to the depth of sleep (0, awake state; 3, shallow sleep; 5, deep sleep) and read using the ClockLab software (Actimetrics, Wilmette, IL, USA). Chi-square periodogram analysis was used to obtain the maximum QP value observed at approximately 24 hours. Record of menstruation and determination of ovulation day The day of menstrual flow was recorded as the menstrual period, according to the participants' self-reports. The day of ovulation was identified using an ovulation day prediction test (Do-Test LH II). The day after the detection of the LH surge was the day of ovulation. DAta The menstrual cycle stages were defined as the follicular phase from the day after the end of menstruation to the day before ovulation day and the luteal phase from the ovulation day to the day before the start of menstruation. The follicular and luteal phases were divided into stages I and II in the front and back halves, respectively, and the menstrual cycle was divided into five stages: the menstrual phase, follicular phase I, follicular phase II, luteal phase I, and luteal phase II (Figure 3). If the number of days was odd when bisecting the follicular and luteal phases, the number of days in follicular/luteal phase II was one day more than the number of days in follicular/luteal phase I (e.g., if the follicular phase was 9 days, follicular phase I was 4 days, and luteal phase II was 5 days).

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