The relationship between cold sensitivity and menstrual cycle in Japanese women under normothermic conditions

Abstract

Background

Many Japanese women report experiencing sensations of cold in their daily lives. We conducted a two-part study to determine whether the common complaint of coldness changes with menstrual cycle in women.

Methods

In the first part of the study (Part 1), we conducted an Internet survey that included 627 women aged 15 to 69 years. Participants answered a questionnaire about the relationship between coldness and menstrual cycle. The questions regarding coldness were used to classify participants into a cold-sensitive group (C group, n = 273) and a normal group (N group, n = 354). In the second part (Part 2), we surveyed 20 young adult women (C, n = 10; N, n = 10) on the cold sensation of 11 body parts. Furthermore, we tested cold sensitivity in the luteal and follicular phases at room temperature (25 ± 1 °C). Cold sensitivity was evaluated by calculating the slope of the relationship between thermal sensation and hand skin temperature during hand cooling in water (from 31 °C to 23 °C).

Results

In Part 1, no association was found between the number of applicable coldness-related questions and age. The highest percentage of respondents in both groups answered that “coldness is not related to menstruation” (C, 64.8%; N, 48.0%). In Part 2, no difference was found in the cold sensations at 11 body sites between the luteal and follicular phases in the C and N groups; however, a decrease in sublingual temperature (-0.28 ± 0.22 °C) was noted at the onset of the follicular phase. The cold sensations at 31 °C in the precooling period were significantly stronger in the C group than the N group under both menstrual cycle conditions, whereas cold sensitivity in the hand was similar between the luteal and follicular phases in both groups.

Conclusions

These findings suggest that changes in body temperature with menstrual cycle do not affect overall cold sensation or hand cold sensitivity, regardless of the presence or absence of cold constitution, under normothermic conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12905-025-04050-1.

Introduction

There are many individuals who complain of feeling cold in their daily lives, regardless of the season. In Japan, some women report pronounced localized chilliness in specific body regions under temperate thermal conditions when most individuals do not perceive cold [1–4]. A cold constitution with higher sensitivity to cold sensations is called “hi-e-sho” in Japanese, which is frequently accompanied by stiff shoulders, headaches, swelling, or insomnia [1–4]. Moreover, women with cold constitution tend to have severe menstrual symptoms [5, 6]. Because cold sensitivity is commonly seen in young adult women after puberty, a link to female hormones has been suggested [6, 7].

In an epidemiological study in a Swiss urban population aged 20–40 years [8], thermal discomfort with cold extremities occurred at the highest intensity in younger, slimmer women and at the lowest intensity in elderly, stouter men. In an epidemiological survey of women visiting a gynecology and obstetrics clinic [9], 52.0% reported feeling cold. In addition, they reported that the frequency was below 30% among women in their early 40 s, but increased to over 40% after menopause, when female hormone levels decline, and exceeded 50% among women aged 55 or older. There is no consensus regarding the relationship between sensitivity to cold and age.

When examining sensitivity to cold in menstruating adult women, it is necessary to consider the influence of the menstrual cycle. Due to the fluctuation of female hormones in the ovarian cycle, core body temperature decreases with the onset of the follicular phase and increases with the onset of the luteal phase [10–12]. Female hormones also affect peripheral vasomotion, and the digital vasoconstrictor response to local cooling increases during the luteal phase when progesterone levels increase [13]. During the follicular phase when core body temperature drops, the whole body may feel colder than during the luteal phase. Otsuka et al. [14] examined the relationship between cold sensitivity, as assessed by local skin cooling, and the ovarian cycle. They reported that the cold sensitivities in the cheeks and abdomen were higher in the follicular phase, when the core body temperature was lower than in the luteal phase. On the other hand, Matsuda-Nakamura et al. [15] reported that cold sensitivity, assessed by whole-body cooling, was not affected by changes in core body temperature associated with the menstrual cycle. Thus, no consensus about the relationship between coldness and the menstrual cycle has been reached. Moreover, previous studies have not examined the relationship from the perspective of the presence or absence of cold constitution. We hypothesized that if there is an effect of menstrual cycle on cold sensitivity, this effect would be more evident in women with cold constitution.

In this study, we conducted epidemiological (Part 1) and experimental (Part 2) approaches to investigate the relationship between cold sensitivity and menstrual cycle in adult women with and without cold constitution. In Part 1, we conducted a questionnaire survey of women with a wide age range (15–69 years old) to get an overview of whether complaints of cold in daily life are related to the menstrual cycle and whether they change with menopause. In Part 2, we compared cold sensations in the luteal and follicular phases in female adults with normal menstrual cycles. We investigated whether sensitivity to cold, which is common among women, was enhanced during the menstrual period when a drop in sublingual temperature was observed.

Methods

Participants

In Part 1, the participants were 627 healthy women aged 15–69 years. Participants were recruited from a pool of 3.82 million research monitors across Japan by an internet research company (INTAGE Research Inc., Tokyo, Japan). By age group, 104 participants were aged 15–19 years (teens), 102 were aged 20–29 years, 108 were aged 30–39 years, 105 were aged 40–49 years, 105 were aged 50–59 years, and 103 were aged 60–69 years. The participants were divided into two groups based on a 10-question interview reported previously [16]. The interview consisted of the following questions: (1) Are you sensitive to a reduction in environmental temperature? (2) Do you feel colder in a cold environment than others do? (3) Do you sometimes feel cold even in summer? 4) Do you dislike being barefoot even in summer due to coldness? 5) Do you feel cold in an air-conditioned room in summer when most people feel comfortable? 6) Do you need thicker clothes than others do? 7) Do you need an electric blanket for better sleep in winter? 8) Do you wear socks while sleeping in winter? 9) Do you often wake up due to coldness or cold extremities in winter? 10) Do you often have pain or color changes in the fingertips or toes due to bad circulation in cold? Participants who answered yes five or more times in the interview were divided into a cold-sensitive group (C group, n = 273), whereas those who answered yes four or fewer times were divided into a normal group (N group, n = 354). The reliability and validity of the questionnaire in screening women with cold constitution were confirmed in a previous study [17].

In Part 2, the participants were 20 healthy adult women aged 20–22. The participants were divided into a C group (n = 10) and an N group (n = 10) using the same criteria based on the same 10-question interview used in Part 1. None of the participants were using contraceptives. All participants had regular menstrual cycles. All the participants in the C group and none of the participants in the N group were aware of sensitivity to cold. The groups had similar height (C group, 156.5 ± 4.5; N group, 158.3 ± 4.1 cm), weight (51.0 ± 6.6; 56.2 ± 9.6 kg, respectively), and body mass index (20.8 ± 2.1; 22.4 ± 3.5, respectively).

The study was conducted in accordance with the Declaration of Helsinki. The purpose, methods, and risks of the experiment were sufficiently explained to the participants beforehand. In Part 1, informed consent was obtained by the voluntary answer of the questionnaires. In Part 2, written consent forms were received from all the participants. An ethical statement (Approval No. 2023-33) was obtained from the Bioethics Committee of Yamaguchi Prefectural University, Japan.

Protocol, measurements and parameters

Part 1

The items in the Internet survey consisted of: sex, age, 10 questions on body coldness to identify coldness [16], and one question on menstrual cycle and coldness. The question on menstrual cycle and coldness asked respondents to choose one time of the menstrual cycle when they feel cold most, with six choices: “before menstruation,” “during menstruation,” “after menstruation,” “don’t feel cold,” “not related to menstruation,” and “no menstruation, and no desire to answer.” Part 1 was conducted in the fall (November) using monitors from all over Japan.

Part 2

Experiments involving the hand cold sensitivity test were conducted once each during the period 2–10 days before menstruation (luteal phase) and 2–6 days after the onset of menstruation (follicular phase) (two times total), at the same time (between 11:00 and 15:00). Half of the participants in each group performed the experiment in the luteal phase first, whereas the other half performed the experiment in the follicular phase first. To determine the experimental date, the next menstrual onset date was predicted based on menstrual records for the previous three months. During the approximately 4-week experiment, waking basal body temperature was recorded daily. The menstrual cycle was determined from changes in basal body temperature, menstrual flow, and urinary luteinizing hormone test kits (Clearview Easy LH, Abbott).

The experiment was conducted in a laboratory set up at a room temperature of 25 ± 1 °C and a humidity of 50 ± 10%. After answering about the thermal sensation for each region of the body, subjects were placed in a supine resting position on a bed for 10 min. During this rest period, sublingual temperatures and skin temperatures (Tsk) at four sites (left dorsal finger, left dorsal hand, left dorsal toe, and left dorsal foot) were measured. The subject was then placed in a sitting position on the bed and a cold sensitivity test was performed. In this test, subjects placed their left hand in 31 °C water in a thermostatic bath for 5 min to maintain Tsk at a constant level, followed by a decrease in water temperature from 31 °C to 23 °C in 9 min (approximately − 0.9 °C/min). During this time, temperature, cold sensation, and Tsk in the hand were continuously measured. All experiments in Part 2 were conducted between January and April.

A questionnaire survey concerning thermal sensation in 11 regions of the body (arm, abdomen, hand, fingertip, foot, toe tip, neck, shoulder, back, lower back, and buttocks) was scored using the following scale: “3. feel strong coldness”, “2. feel coldness”, “1. feel coldness a little”, “0. not at all”, “−1. feel hotness a little”, “−2. feel hotness”, and “−3. feel strong hotness” [18]. Sublingual temperature was measured under the tongue using a women’s electronic thermometer (MC-6830 L, Omron Healthcare). For measurement of Tsk, a thermistor sensor (ITP082-24, Nikkiso-Thermo) was fixed to the skin surface using surgical tape, and Tsk was measured every second using a high-precision temperature measurement device (NT Logger N543RV, Nikkiso-Thermo).

During the cold sensitivity test, Tsk, water temperature in the thermostatic bath, and thermal sensation were measured. The measurement sites for Tsk were the left dorsal finger area and the dorsal hand to be immersed in the water. To measure thermal sensation, we used a device based on the visual analog scale (VAS) [19]. The device had a knob that could be moved 15 cm to the left and right, and the output value of the voltage varied according to its position. A position 2.5 cm from the left end was considered “very cold” and a position 2.5 cm from the right end was considered “neither warm nor cold.” Participants were allowed to move an additional 2.5 cm to the left or right beyond 10 cm, the width between the two sensations, for sensations beyond “very cold” or “neither warm nor cold.” The device for measuring thermal sensation was placed in front of the subject where it was easy to move the knob with the right hand during the measurement and where arm movements were as small as possible.

Data analysis and statistics

Means ± SD of all measurement items were calculated. In Part 1, to examine differences in cold symptoms by age group, participants were classified into six age groups (teens to 60–69 years groups). In Part 2, Tsk was averaged over 10 min while resting in a supine position. Tsk and thermal sensation (VAS value converted to length in mm) during the cold sensitivity test were averaged every minute. The average values for the last 3 min of the 5-min period were calculated as the baseline value at a water temperature of 31 °C. The values of the cooling period were calculated from the averages for the 9-min period of cooling. Tsk in the hand was defined as the average Tsk of the dorsal finger and the dorsal hand. A regression equation was calculated using the least squares method from the relationship between Tsk in the hand and VAS values while the water temperature was decreasing, and the regression coefficient was used as an index of cold sensitivity.

A repeated two-way analysis of variance was performed to test the difference between the experimental conditions (groups and generation, groups and menstrual cycle) in each measurement item. Bonferroni multiple comparison test was performed as a post hoc test when the main effect was significant. Effect sizes were reported as eta-squared (η²). A chi-square test was used to compare proportions. The null hypothesis was rejected at the level of p < 0.05.

Results

Part 1

Figure 1 shows the number of applicable items among the 10 questionnaire items related to coldness in each age group. The number of applicable items was significantly higher in group C than in group N in all age groups (p < 0.001); however, no difference was observed between generations in any groups. The proportion of people in group C among all participants was 37.5% in the group aged 15–19, 50.0% in the group aged 20–29, 49.1% in the group aged 30–39, 46.7% in the group aged 40–49, 37.1% in the group aged 50–59, and 40.8% in the group aged 60–69. No significant differences were found among the groups.

Fig. 1.

Number of applicable items by age group in the cold-sensitive group (C group) and the normal group (N group) in Part 1. * p < 0.05 vs. N group

Figure 2 shows the relationship between the menstrual cycle and subjective symptoms of coldness by group. In both groups, the most common answer was “not related to menstruation” (C, 64.8%; N, 48.0%). When recalculated among those who felt cold, the proportion of people who answered that cold was “not related to menstruation” was similar between the C group (78.7%) and the N group (82.1%). The proportion of people who “never feel cold” was significantly smaller in the C group than in the N group (p < 0.001). There was no difference between the groups in the proportion of people who replied “no menstruation, and no desire to answer.”

Fig. 2.

Percentage of people who chose each option for question related to menstrual cycle and coldness in the C (n = 273) and N (n = 354) groups in Part 1

Part 2

Based on the subjects’ self-recorded menstrual cycles over the past three months, there was no significant difference between the C group (29.7 ± 2.3 days, range 28–34 days) and the N group (29.4 ± 2.8 days, range 25–35 days). There was no significant difference in the menstrual days during the experiment period between the two groups (C, 6.5 ± 1.2 days; N, 6.1 ± 1.2 days).

In both groups, the sublingual temperature was lower (F = 38.807, p < 0.001, η² = 0.000) in the follicular phase (C, 36.5 ± 0.1 °C; N, 36.6 ± 0.2 °C) than in the luteal phase (C group, 36.9 ± 0.1 °C; N group, 36.8 ± 0.2 °C). There were no differences in sublingual temperatures (F = 0.012, p = 0.915, η² = 0.504) between the groups in any menstrual cycle conditions. There were no differences in Tsk in the hand (F = 0.007, p = 0.932, η² = 0.000) between the luteal phase (C, 34.2 ± 1.1 °C; N, 34.2 ± 0.9 °C) and the follicular phase (C, 34.2 ± 0.9 °C; N, 34.2 ± 1.2 °C) (F = 0.005, p = 0.946, η² = 0.000) between the groups. Furthermore, foot Tsk showed no difference (F = 0.034, p = 0.856, η² = 0.001) between the luteal phase (C, 28.5 ± 2.4 °C; N, 31.3 ± 3.1 °C) and the follicular phase (C, 29.5 ± 3.4 °C; N, 30.6 ± 3.6 °C), while it was lower in the C group than the N group (F = 4.681, p = 0.037, η² = 0.112).

In the precooling baselines of cold sensitivity test (Fig. 3), there were no differences in Tsk in the hand between groups or between follicular and luteal phases. On the other hand, the VAS values were lower (p < 0.05) in the C group than in the N group under each menstrual cycle condition. In all experimental conditions, Tsk in the hand decreased as the water temperature decreased, and the VAS values decreased with decreasing Tsk in the hand (Fig. 3, upper panel). When Tsk or VAS values were averaged throughout the cooling period, the averaged Tsk was similar between the two groups, whereas the averaged VAS values were lower (p < 0.05) in the C group. A significant positive correlation (r = 0.905–0.998) was found between Tsk in the hand and VAS values in all experimental conditions, whereas the regression line was lower in the two conditions for the C group than in the follicular phase for the N group (Fig. 4). The regression coefficient, an index of cold sensitivity in the hand, did not differ (F = 3.000, p = 0.092, η² = 0.075) between the luteal phase (C, 10.2 ± 4.0 mm/°C; N, 9.7 ± 2.5 mm/°C) and follicular phase (C, 11.5 ± 5.0 mm/°C; N, 9.7 ± 3.6 mm/°C) in either group, and no differences were observed (F = 0.714, p = 0.404, η² = 0.018) between groups in any conditions.

Fig. 3.

Changes in skin temperature in the hand and thermal sensation during hand cooling tests in the luteal and follicular phases in the C (n = 10) and N (n = 10) groups in Part 2 * p < 0.05 vs. N group

Fig. 4.

Relationship between skin temperature in the hand and thermal sensation during hand cooling tests in the luteal and follicular phases in the C and N groups in Part 2

Figure 5 shows the thermal sensation in each region of the body in the C and N groups by menstrual cycle conditions. In both luteal and follicular phases, the C group felt colder (F = 12.434–20.813, p = 0.000-0.001, η² = 0.247–0.365) than the N group in the hands, fingertips, feet, and toes, whereas no differences were observed (F = 0.097–1.920, p = 0.174-1.000, η² = 0.000-0.050) between the groups in thermal sensation of other parts of the body. In both groups, there was no significant difference in thermal sensation of each body part between luteal and follicular phases (F = 0.037–1.630, p = 0.210–0.849, η² = 0.001–0.032).

Fig. 5.

Thermal sensations in eleven regions of the body in the luteal and follicular phases in the C and N groups in Part 2. * p < 0.05 vs. N group

Discussion

Many women are aware of feeling cold in their daily lives. In a survey conducted on 470 adult women [20], 63.6% were aware of feeling cold. Furthermore, Shibahara and Ito [21] reported that 50.6% of healthy women responded that they “have cold constitution.” Based on the criteria in this study (satisfying five or more of the ten questions regarding coldness), 43.5% of the total participants were identified as having cold constitution, confirming that many women aged 15 and over experience discomfort associated with cold. It has been reported that women with cold constitution not only suffer from discomfort due to cold but also have a high tendency to have menstrual abnormalities [22] and complaints such as insomnia [23]. Thus, cold constitution reduces the quality of life in women. In this study, epidemiological and experimental approaches were conducted on women aged 15 to 69 years old to clarify the relationship between body coldness and menstrual cycle. The results showed that: (1) the majority of respondents with and without cold constitution in Part 1 stated that complaints of cold were unrelated to menstrual cycle, (2) in the participants in Part 2, there was no difference in cold sensitivity in the hand in the luteal and follicular phases, and (3) in a normal temperature environment in Part 2, the participants with cold constitution were more likely to feel cold in the peripheral parts of their body than the women without cold constitution, and that the tendencies were not dependent on menstrual cycle.

In Part 1, among women who felt cold in their daily lives (225 women in C, 207 women in N), the percentages of those who thought that it was “not related to menstruation” were about 80% in both groups. This supports a previous survey of 180 postmenopausal women aged 50 years or older that reported that the proportion of women with cold constitution did not change with age and was not related to serum concentrations of gonadal hormones [24]. Although this study did not include the answer “I do not menstruate,” it is assumed that women in their 60 s had already gone through menopause. As there was no difference in the proportion of women in their 60 s who suffered from coldness compared to other age groups, this indicates a negative result regarding the involvement of menstrual cycle in cold sensitivity.

Koyasu et al. [25, 26] reported that more than 70% of pregnant women were aware of cold constitution when not pregnant, and that about 60% continued to suffer from it during pregnancy. They also reported that the prevalence of dizziness, dry mouth, lower back pain, coldness after pregnancy, and frequent urination was significantly higher in pregnant women who were aware of cold constitution when not pregnant. As symptoms of coldness continued even during pregnancy, when menstruation temporarily stops, this suggests that menstruation and the associated drop in core body temperature are not directly involved in the increase in complaints of sensitivity to cold. When comparing the percentage of people who felt cold in the three conditions of before, during, and after menstruation, the percentage was small at less than 10% in each condition; however, the responses of “during menstruation” were higher in both groups (C: 7.7%; N: 8.2%). Thus, there are individual differences in the timing of feeling cold before, during, and after menstruation in some women, and there is a tendency for coldness to be more common in the follicular phase. However, it should generally be considered that there is a low correlation between complaints of coldness and menstrual cycle.

In Part 2, an expected drop in sublingual temperature was observed in the follicular phase compared with the luteal phase. Our findings support a previous study [27] that reported no difference between the two phases in Tsk of the foot and hand. They reported that the general Tsk of women is not altered due to exogenous hormones, menstrual cycle phase, or menopause, and that Tsk tends to be lower in regions with an accumulation of adipose tissue. Regarding the sensation of coldness in the 11 regions of the body investigated in Part 2 (Fig. 5), the sensations of coldness in the hands, fingertips, feet, and toes were significantly higher in the C group than in the N group in both luteal and follicular phases. A previous study reported that the cold sensation threshold in the dorsum of the hand, dorsum of the foot, and lower back was significantly lower in those with cold constitution, suggesting high cold sensitivity in these areas [28]. Our previous studies [29, 30] also reported that the sensation of coldness in the distal parts of limbs in a normal temperature environment is more pronounced in women with cold constitution; however, this study provides new evidence that the differences in cold sensation in different regions of the body are not related to the drop in core body temperature that accompanies the onset of menstruation.

During the cooling test in Part 2, there was no difference in the Tsk of the hand immersed in 31 °C water between the C and N groups; however, the C group reported that the thermal sensation felt colder (Fig. 3). These results indicate that the hand Tsk threshold producing the same cold sensation is higher in the C group than in the N group under normothermic conditions. In both groups, no difference was observed in the thermal sensations at a similar Tsk of the hand in the luteal and follicular phases, which is consistent with the results of a survey on regional differences of coldness (Fig. 5).

When cold sensitivity was evaluated from the slope of the regression line of the relationships between the thermal sensation and the Tsk of hand, there was no difference in the cold sensitivity in the luteal and follicular phases, regardless of whether the participants had a cold constitution. Matsuda-Nakamura et al. [15] reported no difference between the luteal and follicular phases in systemic and peripheral cold sensitivity assessed by changes in thermal sensation in response to decreases in mean Tsk, finger Tsk, and hallux Tsk during a decrease in room temperature. Although the methods for evaluating cold sensitivity were different, the results of this study are consistent with their findings.

Otsuka et al. [14] evaluated warm- and cold-sensation thresholds in nine regions (each 6.25 cm²) during the menstrual cycle using a heat flux-type warm/cold sensation threshold meter. They reported that the warm-sensation threshold was not influenced by the menstrual cycle in any region, but the cold sensation thresholds of the cheeks and abdomen were higher during the luteal phase than the follicular phase, indicating reduced cold sensitivity. As salivary progesterone concentrations are positively correlated with cold sensation thresholds, Otsuka et al. hypothesized that elevated progesterone levels during the luteal phase decrease cold sensitivity. However, the mechanisms underlying the site-dependent effects of female hormones on cold sensitivity remain to be elucidated. These findings suggest that progesterone reduces cold sensitivity in a site-dependent manner, leading to decreased sensory responsiveness in certain regions during the premenstrual luteal phase. However, in Part 2, the thermal sensations in 11 regions of the body were not significantly different between the two menstrual cycle conditions (Fig. 5). Cold sensation is generally influenced by habituation to cold stimuli [31]. However, in the study by Otsuka et al., the order of measurements for the luteal and follicular phases was not specified, leaving the potential influence of habituation to thermal stimuli unresolved. The findings of the present study suggest that, under normal living conditions, cold symptoms in many women are not directly dependent on the menstrual cycle or on decreases in core temperature associated with the onset of menstruation.

Yamazaki and Sone [32] reported that cold sensitivity, as determined from thermal sensation when foot skin was locally cooled from 35 °C to 25 °C, was significantly higher in female participants with cold constitution than in those without. They found that cold sensation at 35 °C of foot Tsk before cooling was similar in the participant groups, suggesting that cold sensitivity evaluated from the slope of the relationship between Tsk and cold sensation is influenced by the levels of thermal sensation in the precooling baseline. In other words, there remains the possibility that the degree of influence of differences in cold sensitivity between groups may vary depending on the region of the body evaluated and the methods of cooling stimulation. The results of this study suggest that the Tsk-thermal sensation relationships in participants with cold constitution were shifted toward a stronger cold sensation than those without cold constitution, and that the slopes of the relationships in both groups were not affected by the menstrual phase, when the core body temperature decreased.

Limitations of the study

This study had several limitations. First, plasma estrogen and progesterone were not measured in Part 2. In young adult women with normal menstrual cycles, female hormone concentrations are low during menstruation during the early follicular phase, whereas they are relatively high during the luteal phase; however, this study did not assess the role of female hormones in cold sensitivity. Second, the number of subjects in Part 2 was determined empirically based on feasibility, and no a priori power analysis was conducted. A group size of 10 subjects is relatively small, but it was considered minimally acceptable for experimental studies. Third, “hi-e-sho” is a socially accepted concept in Japan; however, no medical diagnostic criteria have been established, and it remains unclear whether it can be applied to populations outside Japan. Studies from non-East Asian populations have reported that cold symptoms and strong peripheral skin vasoconstriction were more prevalent in women than in men in healthy subjects [8, 33, 34] and patients with Raynaud’s phenomenon [35]. Thus, our findings on the relationship between the menstrual cycle and cold sensitivity may also be applicable to women outside East Asian populations.

Significance and implications of the findings

Since discomfort associated with chilliness reduces quality of life, it is important to clarify its causes and countermeasures. To mitigate the symptoms of cold constitution, ingestion of foods with a body-warming effect, such as ginger and long pepper (Piper longum L) [36, 37]; foot massage [38]; and aerobic exercise [30] have been reported to be effective. The results of this study suggest that the optimal timing for implementing these measures is unaffected by the menstrual cycle. However, while considering the severity of menstrual-related symptoms other than coldness, measures to prevent cold hypersensitivity are necessary in women with a cold constitution.

In conclusion, we found: (1) the prevalence of cold constitution in adult women was independent of age (15 to 69 years old); (2) the degree of coldness in daily life was not related to menstrual cycle, regardless of whether the participant has cold constitution or not; and (3) the thermal sensation of the trunk and extremities and the cold sensitivity of the hands in a normal temperature environment are not affected by the decrease in core body temperature that accompanies menstruation, regardless of whether the participant has cold constitution or not.

Abbreviations

C group

Cold-sensitive group

N group

Normal group

Tsk

Skin temperature

VAS

Visual analog scale

n

Number of participants

r

Correlation coefficient

Authors’ contributions

The study was designed by FY. Acquisition of the data was carried out by FY, MT, HK, and YF. Analyses and interpretation of data was done by FY, MT, HK, and YF. Drafting the manuscript was done by FY, MT, HK, and YF. Revising the manuscript critically for important intellectual content was done by all the authors. All authors read and approved the final manuscript.

Funding

This study was supported by JSPS KAKENHI Grant Number 25K14772 and Yamaguchi Prefectural University Joint Research Promotion Program.

Data availability

Datasets generated and/or analyzed in the current study are presented in the text.

Declarations

Ethics approval and consent to participate

The study was conducted in accordance with the Declaration of Helsinki. Informed consent to participate was obtained from all of the participants in the study. Ethical statement (approval number 2023-33) was obtained from the Bioethics Committee of Yamaguchi Prefectural University.

Consent for publication

There are no identifiable details included.

Competing interests

The authors declare no competing interests.