As cold hypersensitivity is commonly reported by women in adolescence and early adulthood [5]-[7], this study recruited 116 female university students from Kumamoto University. The purpose and procedures of the study were explained orally and in writing, and written informed consent was obtained. The participants were assured that the data would be anonymized and used solely for analytical purposes.

2.2.1. Subjective Assessment

A self-administered questionnaire on cold symptoms was administered, referencing prior studies on cold hypersensitivity, autonomic function, and peripheral circulation [2]-[5][7]-[12]. The menstrual cycle phase was not controlled for during data collection.

2.2.2. Objective Assessment

Autonomic and cardiovascular function, blood pressure, and peripheral skin temperature were measured. Peripheral circulation and autonomic activity were assessed using a non-invasive device (“Body Checker,” Tokyo Iken Co., Ltd., Japan). This device estimates circulatory indices using impedance plethysmography and pulse wave analysis, combined with heart rate variability-based algorithms. Vascular elasticity is calculated from pulse wave characteristics reflecting arterial compliance, while cardiac output strength (stroke volume-based index) is primarily derived from estimated stroke volume.

A heart rate variability (HRV) analysis was used to derive indices of sympathetic and parasympathetic activity, following established recommendations [14][15]. Peripheral circulation indices included stroke volume, vascular elasticity, and residual blood volume [14].

Blood pressure was measured with an upper-arm sphygmomanometer (HEM-7500F; Omron Healthcare, Japan) using standardized procedures.

The index finger was immersed in water at 10˚C for 1 min. Skin temperature was measured immediately after immersion and at 5 min and 10 min post-immersion using an infrared thermometer (Fluke Connect, USA) to assess the recovery of peripheral temperature regulation [14].

Chi-square tests, Mann-Whitney U tests, and Welch’s t-tests were applied, with p < 0.05 considered significant. The graph values were rounded to one decimal place.

All procedures were approved by the Ethics Committee of Epidemiological Studies at Yamagata Prefectural Yonezawa University of Nutrition Sciences and Kumamoto University. All the data were anonymized to protect privacy.

A total of 116 female university students were enrolled in the study. Using the diagnostic criteria [12], 92 participants (79.3%) were classified as having cold hypersensitivity (CH) and 24 (20.7%) as non-cold hypersensitivity (NCH). Although the proportion of CH increased with age, chi-square tests revealed no significant differences among age groups (p ≥ 0.05). Relative to the NCH group, the CH group had a significantly higher mean age (p < 0.05) and lower BMI (p < 0.05). Height and diastolic blood pressure were comparable, whereas systolic blood pressure was modestly higher in the NCH group (Table 1).

Table 1.Basic characteristics.

^†Welch’s t-test; ^‡Mann-Whitney test; n.s., not significant.

The prevalence of each diagnostic item is summarized in Table 2. In the CH group, “Hands and feet colder than others,” “Coldness in waist, hands, or feet causing discomfort,” and “Consider oneself more sensitive to cold than others” were most frequently endorsed. In the NCH group, “frequent urination on cold days” and “the use of electric blankets or hot packs during winter” were common.

Table 2.Prevalence of diagnostic items for cold hypersensitivity.

Note. The key and reference items were defined according to the report of Sakaguchi et al.

Among the CH group (n = 92), 72 participants (78.3%) reported recognizing themselves as having cold hypersensitivity, while 20 (21.7%) did not. Only one participant (4.1%) in the NCH group (n = 24) reported perceiving herself as cold-hypersensitive.

Supplementary questions were asked of participants who both belonged to the CH group and recognized themselves as cold-hypersensitive (n = 72). Table 3 presents the main findings.

Extremity cold was the most common reason for self-recognition (70.8%).Onset typically occurred during adolescence (mean 15.0 years).Cold was most often localized to the feet (87.5%) and hands (84.7%) and most frequently occurred in winter and at bedtime.

Table 3.Characteristics of self-aware CH participants.

A greater proportion of participants in the CH group (73.9%) reported taking countermeasures than the NCH group (37.5%) (Table 4). The CH participants most frequently used socks, layered clothing, hot packs, and warm drinks. Participants in the NCH group used heating devices and futons more often.

Table 4.Countermeasures against cold.

“Any countermeasures” indicates the proportion of participants reporting at least one countermeasure. Percentages for specific subcategories were calculated independently and therefore may exceed the value for “Any countermeasures.”

Seventeen autonomic symptoms were assessed in this study (Table 5). The mean number of symptoms per person was higher in the CH group (3.2) than in the NCH group (2.2) (p < 0.05). Both groups reported stiff shoulders and morning weakness. Coldness or numbness of the extremities was more frequent in the CH group (41.3%) than in the NCH group (4.2%).

Table 5.Autonomic symptoms and mean number of symptoms.

Autonomic balance differed between groups (Table 6). Participants in the CH group more often showed sympathetic predominance, whereas parasympathetic predominance was more frequent in the NCH group. The stress scores did not differ significantly between the groups (Table 7 and Table 8).

Table 6.Autonomic balance in the CH and NCH groups.

Table 7.Stress symptoms in the CH and NCH groups.

Table 8.Stress scores in the CH and NCH groups.

Four indices of blood circulation (cardiac output strength (stroke volume-based index), vascular elasticity, residual blood volume, and vascular stage) were measured using a Body Checker device. No statistically significant differences were observed between the CH and NCH groups (Mann-Whitney test, p > 0.05). Table 9 presents the distribution of each index.

To evaluate the peripheral circulatory function, a cold-water load test (10˚C, 1 min) was performed. Baseline fingertip temperature was significantly higher in the CH group (24.9˚C ± 2.6˚C) than in the NCH group (24.0˚C ± 1.5˚C) (p < 0.05, Welch’s t-test) (Table 10).

The temperature-recovery curves are shown in Figure 1. At 10 min post-immersion, the NCH group recovered above the baseline, whereas the CH group did not reach baseline levels.

Table 9.Indices of blood circulation in the CH and NCH groups.

Table 10.Mean fingertip skin temperature before cold water load (˚C).

Figure 1.Recovery of fingertip skin temperature after cold-water load.

The distribution of the recovery rate categories is presented in Table 11. Poor recovery (<90%) was observed in 20.6% of the individuals in the CH group and 4.2% of the individuals in the NCH group. The recovery patterns are shown in Figure 2.

Table 11.Distribution of recovery rate at 10 min after cold water load.

Figure 2.Skin temperature recovery patterns in good vs. poor recovery groups.

Welch’s t-test showed a significant difference (p < 0.05), with a higher baseline temperature in the CH group relative to the NCH group.

Cold hypersensitivity group: 24.9˚C (before), 20.0˚C (immediately), 23.7˚C (5 min), 24.1˚C (10 min).

Non-cold hypersensitivity group: 24.0˚C (before), 20.5˚C (immediately), 24.6˚C (5 min), 25.7˚C (10 min).

The subjects with a poor recovery showed a larger immediate temperature drop and incomplete recovery after 10 min. Subjects with a good recovery exhibited a smaller temperature drop and reached near or above the baseline by 10 min.

Cold hypersensitivity was observed in 79.3% of participants, which was higher than the estimated prevalence in community-based and student samples that typically range around 40% - 60% among women [14][15]. Most cold-sensitive participants were aware of the symptoms (78.3%) and reported discomfort (80.5%). In addition, previous research indicated that menstrual pain may enhance sensitivity to cold and pain perception, which could partly explain the heightened prevalence among young women [17]. This may partly reflect selection bias, as participants were university students who volunteered for a health-related survey and were classified using questionnaire-based criteria, which may overestimate prevalence compared with population-based studies.

Lower BMI in the CH group may reduce the basal metabolic rate and exacerbate peripheral cold sensation. Reduced subcutaneous fat further increases the heat loss. These findings are consistent with reports linking lower BMI and reduced subcutaneous fat with greater cold sensitivity [12][14].

A higher autonomic symptom burden, together with sympathetic dominance and reduced parasympathetic activity, suggests impaired peripheral circulation. This pattern aligns with prior studies showing vagal withdrawal and sympathetic predominance in women with hiesho and in young women reporting cold hypersensitivity [13][17]. Furthermore, sex differences in autonomic regulation have also been reported as contributing factors [8]. The significantly lower systolic blood pressure observed in the CH group may reflect mild hypotension associated with autonomic imbalance, a feature commonly reported in individuals with hiesho. Reduced sympathetic vasomotor tone may contribute to both lower blood pressure and impaired peripheral thermoregulation.

Although this study did not find a direct association between self-reported stress and cold hypersensitivity, psychological stress is known to disturb autonomic balance and could indirectly exacerbate cold sensitivity [12][17].

Group differences were not observed for most hemodynamic indices; however, the higher proportion of reduced vascular elasticity in the CH group may contribute to peripheral cold sensations [4].

Delayed post-immersion thermal recovery in the CH group, supporting reduced peripheral temperature regulation capacity, in line with prior observations of cold-induced vasodilation dynamics and recovery kinetics in young women [4].

The mean onset around mid-adolescence, with the feet and hands most commonly affected, highlights puberty as a critical window for the onset of CH and suggests opportunities for early education and intervention.

These findings highlight the importance of health education for young women. Practical guidance may include promoting adequate sleep, a balanced diet, physical activity, stress management, and monitoring of excessive thinness related to dieting. In addition, self-care practices, such as layered clothing, use of thermal aids, and bathing, may help alleviate discomfort. Furthermore, warm-water foot-bathing has been shown to enhance parasympathetic activity and peripheral circulation in young women with cold sensitivity [18].