Hazuki Masuda (2nd year doctoral student, Graduate School of Science and Engineering)
Menstrual symptoms cause physical and mental symptoms such as headaches, abdominal pain, irritability, and difficulty concentrating, not to mention the deterioration of interpersonal relationships and reduced labor productivity that accompany these symptoms. The social burden caused by menstrual symptoms, which afflict many women, is estimated at 682.8 billion yen per year, of which labor losses (i.e., missed work and decreased labor pool and quality) are 491.1 billion yen, so support for women's health has become a serious social issue.
Hazuki Masuda, a doctoral student in the Graduate School of Science and Engineering, is tackling the challenge of developing a system for monitoring women's biological rhythms by engaging in interdisciplinary research exchanges that transcend the boundaries between the humanities and the sciences. We interviewed Ms. Masuda about her research, which aims to practically implement new technologies to realize a society where women can work in a healthier manner.
Toward the development of a system to quantify emotional distress caused by menstruation
Masuda is developing a menstrual cycle monitoring system that combines a subjective evaluation method using qualitative research and a quantitative evaluation method that measures biometric data with a wearable device.
“Until now, the evaluation of emotional distress caused by premenstrual syndrome (PMS) has only focused on the subjective assessment of the evaluator. However, since relying only on the psychological judgments of the evaluators can lead to fluctuations in data and intra-rater variability, going forward, more reliable measurement methods will need to be developed. This is why I am currently working on developing a method that combines subjective and quantitative evaluations.”
When quantifying PMS, it is necessary to estimate the menstrual cycle and ovulation dates. To make these estimations, prediction methods like the basal body temperature method and the calendar method have been conventionally used. These methods present challenges in terms of accuracy and the burden on the user, however.
“The basal body temperature method requires a woman to measure her body temperature at the same time every day for anywhere from dozens of seconds to several minutes upon waking up. This is no easy task for women who are busy with work, housework, and childcare. The calendar method is also difficult to adapt to cycle fluctuations, and while ovulation date prediction tests are highly accurate, the cost of continuously using these tests is high, so for both of these methods, issues remain in terms of factors like accuracy and continuity.”
In recent years, however, the advent of wearable devices has led to the development of more accurate methods that use heart rate or body surface temperature data. That being said, Masuda points out that even taking measurements with wearable devices does not lighten the burden on users.
“Some ovulation date prediction models that use wearable devices boast 90% accuracy, but they are not very user-friendly because they are premised on having a regular daily routine. There is the added issue that these models do not take into account the circadian rhythm*, or our 24-hour biological cycle. Recent studies have shown that 'social jet lag,' which is caused by a mismatch between time spent socializing and circadian rhythms, is one of the factors that worsen PMS, and we need information on circadian rhythms to make more accurate predictions.”
* The 24-hour biological rhythm driven by the internal clock in the suprachiasmatic nucleus of the brain. It is closely related to physical and mental condition.
Development of a high-precision, user-friendly method to measure heart rate during sleep
It has been difficult, however, to implement a monitoring system that takes circadian rhythms into account because monitoring these rhythms requires blood samples, exercise restrictions during the day, and 24-hour measurements. For this reason, Masuda shifted her focus to heart rate during sleep.
“One study that took electrocardiograms of women while they slept and analyzed the data suggested a significant relationship between fluctuations in circadian rhythm amplitudes and the menstrual cycle. Based on the results of this experiment and previous research showing that the heart rate is at its lowest during sleep and, therefore, less sensitive to external stimuli, I came up with the idea, that if we could utilize biological data during sleep, we could develop a method for estimating circadian rhythms that would be less mentally and physically stressful.”
Based on this hypothesis, Masuda proceeded with experiments and succeeded in inferring the nadir of the circadian rhythm from heart rate during sleep. This means it is now possible to measure circadian rhythm fluctuations in a way that is less physically and mentally taxing. Masuda also demonstrated the effectiveness of this method in subsequent experiments measuring the effects of lifestyle changes on circadian rhythms during the COVID-19 pandemic, as well as in experiments estimating menstrual cycles while taking into account social jet lag. With these results, she has found a way to realize a menstrual cycle monitoring system that incorporates circadian rhythm information.
Advancing interdisciplinary research to explore women's health
Masuda has since been selected for the Ritsumeikan University NEXT Fellowship Program, which supports promising, highly motivated doctoral students, and she is a member of a Ritsumeikan Global Innovation Research Organization (R-GIRO) research project called “Development of technology for building human relationships in physical/cyber space using the KOKORO Distance Meter.” Through her work on this project, she interacts with researchers in the fields of psychology, information science and engineering, and life sciences, and is developing an interdisciplinary research perspective. Based on the knowledge she has gained from this project, she is now focusing on improving the accuracy of the monitoring system and developing a device that can measure biological rhythms more simply and accurately.
Going forward, Masuda and her team hope to establish a system that not only helps to alleviate menstrual symptoms, but also contributes to improving performance and eliminating jet lag. In this way, Masuda is tackling social issues while engaging with her fellow researchers, and she is growing every day as a researcher who has come to be indispensable to the development of the research centers and projects in which she is involved.
Admiration for how engineering technology can save lives
Masuda's interest in bioengineering dates back to her elementary school days.
“When I was born, my mother already had a cardiac pacemaker. Ever since I can remember, I have always admired how engineering can save lives, and this is what sparked my interest in engineering.”
After graduating from high school, Masuda entered Ritsumeikan University with the desire to develop medical devices that would help the people around her live healthier lives. While taking her classes, she actively participated in the Ritsumeikan Robot Research Society of Technology (RRST) and deepened her knowledge of robotics.It was an industry-academia-government collaboration project that she joined in her fourth year that helped to broaden her perspective on research.
“It was an interdisciplinary project dealing with support for top athletes. By joining that project, I was able to learn a lot from outstanding experts in various fields, and this led me to want to firmly develop my ability to formulate hypotheses based on evidence and create new things by undertaking repeated experiments.”
Growing by thinking deeply about why certain results are achieved
When we asked Masuda about what she finds appealing about her research, she responded in her typical manner, given that she has thoroughly examined the data and tackled the circadian rhythm monitoring system research project head on.
“I love the process of thinking about why certain results are achieved. It can be a painful process until you generate research outcomes, but this process is what helps me to grow even more. This is what I think makes research enjoyable.”
After completing her doctoral program, Masuda says she hopes to contribute to the world as a healthcare researcher. Her goal is to create a society in which as many people as possible can engage in social activities in a healthy manner.
“I want to help everyone, regardless of age, gender, or disability, to live in good health throughout their lives. In addition to support for women’s health, Japan faces a mountain of other issues, including the cost of social security. My main goal is to use my research to provide people with daily health support and to contribute to preventing disease.”
We expect great things from Masuda’s research, which has the potential to significantly change people’s lifestyles.
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