[Meiji University Educational Corporation] It has been revealed that sleep rhythms change depending on the menstrual stage ~ Pregnancy efforts are now possible with a smart watch! ~
*Meiji University Educational Corporation*
Press release: July 18, 2024
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It has been revealed that sleep rhythms change depending on the menstrual stage ~ You can try to get pregnant with a smart watch! ~ *Research group led by Professor Takahiro Nakamura, Faculty of Agriculture, Meiji University*
* -Key points of research results-*
● The research group led by Professor Takahiro Nakamura of the Animal Physiology Laboratory, Department of Life Sciences, Faculty of Agriculture, Meiji University,
We discovered that the sleep-wake rhythm of healthy women in their 20s changes depending on the stage of their menstrual cycle*1.
● The robustness of the sleep-wake rhythm increases during the follicular phase, which is before ovulation, and
It was found that it decreases during the luteal phase and menstrual period after ovulation.
● The more people have the habit of going to bed late and getting up late, the less robust their sleep-wake rhythm becomes.
It has been shown that people with greater social jet lag (time)*2 tend to have longer menstrual cycles.
●From these results, in the near future, simply wearing a device such as a smart watch will be able to improve your menstrual cycle. It is possible to know the day of ovulation and to try to get pregnant without the need for troublesome measurements.
*1. overview *
A research group led by Professor Takahiro Nakamura of the Animal Physiology Laboratory, Faculty of Agriculture, Faculty of Agriculture, Department of Life Sciences, Meiji University, discovered that the sleep-wake rhythm of healthy women changes depending on the stage of the menstrual cycle.
In women, the menstrual cycle, which is the interval from one menstrual period to the next, completes one cycle (regression) every 28 days on average. During the menstrual cycle, as shown in Figure 1, there are large fluctuations in the blood concentrations of the female hormones estrogen and progesterone. During the follicular phase, which is the period during which the follicle that becomes the source of the egg develops within the ovary, a large amount of estrogen is secreted as the follicle develops, reaching its peak before ovulation. After that, when the egg is ovulated, the body enters the luteal phase, in which a large amount of progesterone is secreted. Fluctuations in female hormones are known to affect the circadian rhythm*3 mechanism that drives sleep-wake rhythms in experimental animals.
In rodents such as mice, which are used as laboratory animals, the daily activity rhythm changes depending on the stage of the estrous cycle, as the estrous cycle returns every 4-5 days. It is known that activity increases and the phase of the rhythm advances, especially at night during proestrus when the blood concentration of estrogen is high. Progesterone also works to weaken the effects of estrogen. This phenomenon is called scalloping because the actogram, a diagram that makes it easy to observe the circadian rhythm, resembles the pattern on a scallop shell (Figure 2).
Until now, scalloping associated with fluctuations in female hormones had not been observed in healthy women. One of the reasons for this is that until now, the only way to record sleep-wake rhythms over a long period of time was to have subjects fill out a sleep diary, a subjective method. With this method, it was difficult to obtain accurate sleep time, and there was no information on sleep depth, so detailed analysis of sleep-wake rhythms was not possible. Using wearable devices that have developed in recent years, it has become possible to objectively acquire and evaluate sleep-wake rhythms over a long period (one year). Therefore*
In this study, we used smartwatches to investigate the influence of menstrual cycles on sleep-wake rhythms in 10 female subjects in their 20s*.
First, we investigated the correlation between the values measured this time. A strong negative correlation was observed between the midpoint of sleep, the time between falling asleep and waking up, and the QP value, which indicates the robustness of the sleep-wake rhythm. Additionally, a strong positive correlation was observed between the number of days in the menstrual cycle and social jet lag (time). These results are *
Healthy women who have a habit of going to bed late and rising late have disrupted sleep-wake rhythms, suggesting that irregular sleep-wake rhythms tend to prolong menstrual cycles*.
Next, we analyzed the sleep-wake rhythm, which changes with the menstrual cycle, and found that the mid-sleep point and QP value change depending on the stage of the menstrual cycle. especially,* QP values, which indicate rhythm robustness, were greater during the follicular phase, when estrogen concentrations are higher, compared to the menstrual and luteal phases*
(Figure 3). These things are observed in rodents etc.* Scalloping is also observed in healthy women*
It means that. Based on this result, we believe that simply by wearing a smart watch, you will be able to accurately determine your menstrual cycle and ovulation day, and in the near future you will be able to get pregnant without the need for troublesome measurements. You can
The results of this research were supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (Project Numbers: 21K06363 and 19K06360) and by the Institute of Science and Technology, Meiji University.
and Biological Rhythms” (Springer Nature; online version dated July 11).
*2. Research background *
The approximately 24-hour rhythm expressed in sleep-wake rhythms, circulatory function rhythms, hormone secretion rhythms, etc. is called the circadian rhythm, and is known to be closely related to female reproductive function in both directions. I am. In particular, the normal return of the menstrual cycle (sexual cycle) is closely related to the circadian rhythm mechanism, and it is known that fluctuations in female hormones associated with the menstrual cycle affect the circadian rhythm.
It was known that sleep structure, which refers to changes in the amount of REM sleep and non-REM sleep that make up sleep, changes during the menstrual cycle. However, the sleep-wake rhythm, which refers to the proportion of sleep in a day,
syndrome:
Changes were reported in women suffering from PMS (PMS), but not in women with stable menstrual cycles and few menstrual-related symptoms or complaints.
In addition, wearable device technology has developed in recent years, and devices such as smart watches that can objectively measure sleep time and sleep depth have become commonplace. This research is unique in that it uses a smartwatch to evaluate sleep-wake rhythms over a long period of time and objectively. We conducted this study thinking that this might enable us to observe scalloping in women.
*3. Impact of this research result on society (significance of this research result) *
In the current situation in Japan, where women are encouraged to participate in society, there is an urgent need for policies to promote women’s health, especially for fertility efforts. This research will provide clues to solving pressing social issues such as the “increasing degree of social change”. Against this background, the main purpose of this study, “Sleep-wake rhythms change depending on the menstrual cycle,” is aimed at elucidating the onset mechanisms of diseases related to circadian rhythms, such as sleep disorders unique to women, and devising preventive measures. It is considered to be an important issue that contributes to society by promoting the establishment of new treatment methods and the development of therapeutic drugs to improve women’s health.
When trying to conceive, it is important to accurately understand your menstrual cycle and ovulation day in order to promote efficient fertilization, but in order to identify the ovulation day, it is necessary to measure and record your basal body temperature every morning using a female thermometer. is needed. It has been pointed out that basal body temperature fluctuates depending on measurement conditions and is not sufficient to accurately determine the day of ovulation. There is also a method of measuring the concentration of luteinizing hormone (LH) in urine using a commercially available ovulation test, but it takes time and effort to purchase and test. The results of this research led to the construction of an algorithm that can identify the day of ovulation simply by wearing a smart watch that is used on a daily basis. By acquiring and analyzing the sleep-wake rhythm that changes with the menstrual cycle using a smart watch, etc., we will be able to develop an app that can accurately and automatically tell you the day of ovulation without any troublesome measurements or tests. In addition, it can be combined with various biological information that can be measured with a smartwatch (body temperature changes, heart rate, blood oxygen saturation, etc.). It is thought that this will enable more accurate prediction of ovulation day. By acquiring large-scale data and building algorithms that incorporate big data analysis, deep learning, etc., it is thought that it will be possible to try to conceive using a smart watch in the near future.
We believe that these results will contribute to the future
development of circadian rhythm (biological clock) research, as well as elucidating the mechanisms of onset of diseases unique to women and devising treatments and countermeasures for them, in addition to fertility efforts. You can This research group will contribute to improving physical and mental health throughout the life course based on circadian rhythms.
*4. Glossary *
*1 “Menstrual cycle”: Refers to the period from the start of menstruation to the day before the start of the next menstruation. In mammals other than humans, it is also called the estrous cycle (estrous cycle). In this case, it refers to the period from ovulation to before the next ovulation. Also called the ovarian cycle, it is a cycle induced by the periodic changes in the ovaries. The length of the menstrual (sexual) cycle varies depending on the animal species, with humans having cycles of 25-38 days, and rodents such as mice having cycles of 4-5 days. In rodents, it is divided into four stages: proestrus, estrus, metestrus, and diestrus; in humans, it is often divided into follicular, ovulation, luteal, and menstrual phases. *2 “Social jet lag”: “Jet lag between weekdays and holidays” caused by the difference between sleep on weekdays when there are social constraints (work, school, housework, etc.) and sleep on holidays without constraints that match the body clock. This refers to “discrepancies in the rhythm of going to bed and waking up.” Research shows that 61% of people in their 20s experience social jet lag of one hour or more.
*3 “Circadian rhythm”: All living things on earth have a body clock function with a cycle of approximately one day (circadian), and follow a basic schedule such as “being active during the day and resting at night.” Physiological functions fluctuate in preparation. Normally, circadian rhythms are regulated on a 24-hour cycle, but in an (experimental) environment where there is no time information, they fluctuate on a cycle of approximately 1 day. The 2017 Nobel Prize in Physiology or Medicine was awarded for the discovery of the molecular mechanism of circadian rhythms.
*5. Notices *
*Published magazine: “Sleep and Biological Rhythms” (Springer Nature) *Paper title: Menstrual variations of sleep-wake rhythms in healthy women *Authors: Tomoko Namie, Tsugumi Kotaka, Kazuto Watanabe, Nana N. Takasu, Wataru Nakamura, Takahiro J. Nakamura
*DOI: 10.1007/s41105-024-00543-y
*URL: https://link.springer.com/content/pdf/10.1007/s41105-024-00543-y.pdf
*Support: This research was supported by the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (Project Number: 21K06363, 19K06360)
It was also conducted as part of the Meiji University Institute of Science and Technology’s focused research.
*Joint research: This research is a joint research with Nagasaki University.
*6. Reference diagrams and explanations *
*Figure 1: Changes in basal body temperature, ovaries, endometrium, and female hormones during the menstrual cycle*
It schematically shows changes in basal body temperature, ovarian condition, endometrial condition, and female hormone concentration during the menstrual phase, follicular phase, ovulation, and luteal phase of the menstrual cycle. Estrogen levels rise in the lead-up to ovulation and decrease after ovulation. Progesterone increases during the luteal phase.
* Figure 2: Actogram of circadian rhythm of circular activity in male (A) and female (B) mice *
The black lines in the figure indicate activities. The vertical axis is days and the horizontal axis is time, which is shown as a double plot of 48 hours. Observations are made under light and dark conditions and constant darkness. Comparing the left and right sides, the right side has a wavy-like activity rhythm. It appears like this because the activity increases and the phase advances during the night (arrow) during the proestrus phase of the sexual cycle, which occurs once every 4 days. This is called scalloping because it resembles the pattern on a scallop shell. This phenomenon is due to the effects of estrogen and progesterone.
* Figure 3: Sleep-wake rhythm of a healthy woman over a one-year period (A) and changes in rhythm robustness depending on the stage of the menstrual cycle (B) *
A: The black line in the diagram indicates sleep. The vertical axis shows the day, and the horizontal axis shows the time. The solid yellow line indicates the day of ovulation. It can be seen that there are variations in the daily sleep-wake rhythm. B:
Rhythm robustness (QP) for each stage of the menstrual cycle was determined from 1 year of sleep-wake data of 10 subjects.
Violin plot diagram for determining the value). QP values were significantly higher during the follicular phase (F1 and F2, red frame) compared to the menstrual phase (M) and luteal phase (L1 and L2).
*Figure 4: Summary of the results of this research*
The diagram schematically shows the sleep-wake rhythm of a healthy man (A) and a healthy woman (B) over a 28-day period. The vertical axis shows the number of days, and the horizontal axis shows the time. The solid black line indicates sleep, and the solid yellow line indicates ovulation days. In men, there are no periodic hormonal fluctuations, so sleep-wake rhythms are not influenced by hormones. On the other hand, this study showed that in women, the robustness of the rhythm increases during the follicular phase when estrogen is high (thick solid line) due to the influence of changes in female hormones associated with the menstrual cycle. This is similar to scalloping seen in rodents.