We created an anonymous questionnaire about hyperhidrosis that was shown in Figure 1. This survey was administered to all patients who visited dermatology department of Gunma university hospital between June 2022 and August 2022. The researcher explained the questionnaire and handed it out to those who accepted to answer. We ended up distributing questionnaires to 1,000 patients.

Patients who refused to answer the questionnaire, infants, and cognitively impaired patients who would have had difficulty completing the questionnaire were excluded.

This study was approved by Gunma University Ethical Review Board for Medical Research Involving Human Subjects (receipt No. HS2022-031, 23 May 2022). This study was carried out after explaining the purpose of the study to each participant. The questionnaire was anonymous and responses to this were considered consent.

Respondents answered the questionnaire (Supplementary Figure S1). Those who answered “yes” to Q1 proceed to the Q2 and Q4. We determine the patients had hyperhidrosis or not by comparing the results of these questions to Hornberger’s diagnostic criteria of primary focal hyperhidrosis [2].

We assessed the severity of hyperhidrosis using Hyperhidrosis Disease Severity Scale (HDSS). Respondents choose the degree of their sweating symptoms (Supplementary Figure S1Q5). In addition, Numerical Rating Scale (NRS) was measured for the degree of disability and discomfort in daytime activities caused by sweating (Supplementary Figure S1Q7).

The questionnaire also included questions about troubled episodes, most uncomfortable season, the frequency of worrying about sweat, the history of treatment, the knowledge about treatment, and the problems with sweat odor (Supplementary Figure S1Q3, 6, 8–11).

We counted the number of patients who met the diagnostic criteria for primary focal hyperhidrosis. The number of each patient diagnosed with hyperhidrosis was summarized in terms of age, gender, area and severity of hyperhidrosis, onset age of hyperhidrosis, complicated skin disease, and treatment history. Complication diseases were categorized by psoriasis, AD, collagenic disease, AA, malignant skin tumor, eczema, others, and unanswered. AD, psoriasis, and AA which were complicated frequently were also tabulated separately. Collagenic disease was excluded because of the suspicion of steroid-induced secondary hyperhidrosis. The parts of hyperhidrosis were listed for head-face, axilla, palmoplantar. The prevalence was calculated by each group.

The chi-square test was used to compare prevalence rates and gender ratios between groups. T-test was used to compare mean age or severity score between two groups. Odds ratios for hyperhidrosis and each complication disease were determined using Fisher’s exact test.

We gave the questionnaire to 1,000 patients and received the answer from 885 (88.5%). The number of patients who complete the criteria of hyperhidrosis were 198 (22.4%) (Figure 1). The male-female ratio was 1:1.35. It was significantly more common in females (P < 0.01) (Figure 2A). Figure 2B shows the age distribution for the entire patient population, and for patients with or without hyperhidrosis. The mean age of patients with hyperhidrosis (51.3 years, SD 15.8) was significantly lower than that of patients without hyperhidrosis (57.2 years, SD 19.1; p < 0.01).

The prevalence rate of hyperhidrosis in each part was 15.1% in head and face, 8.7% in axillary, and 4.6% in palmar and plantar, respectively. The onset of hyperhidrosis in the head and face typically occurred in adulthood (32.2 years, SD 17.7), whereas onset in the palmar and plantar occurred during childhood (13.3 years, SD 9.1) (Table 1).

The prevalence of axillary hyperhidrosis was significantly higher among women (p = 0.02). No gender differences were observed in the prevalence of head/face or palmar/plantar hyperhidrosis (Figure 3A). Moreover, when comparing patients aged ≧40 years with those aged <40 years, the prevalence of head/face hyperhidrosis was significantly higher in the older group (p = 0.01). In contrast, the prevalence of palmar/plantar hyperhidrosis was significantly lower in the older group (p < 0.01), with a mean age at onset as early as 13.3 years (SD 9.1). No age-related differences were observed in the prevalence of axillary hyperhidrosis (Figure 3B).

The aggregate results of HDSS were shown in Figure 4. Over half (54.3%) of the patients complained HDSS 3 or 4, which was considered severe or very severe. No significant difference was seen between head-face, axillary, and palmar-plantar groups in the percentage of patients with HDSS 3 or 4.

In the assessment of sweat-related discomfort on QOL using NRS, the mean score for all patients with hyperhidrosis was 5.87 (SD 2.46).

Next, when we asked about the season during which sweating was perceived as most uncomfortable, most respondents indicated summer (65.2%), followed by all year round (31.3%) (Figure 5). In addition, it was found that only a small number of patients either knew that hyperhidrosis was treatable (13.4%) or had received treatment for them (7.9%).

Finally, the most common skin diseases complicated with patients with hyperhidrosis were psoriasis, AD, collagen disease (Systemic lupus erythematosus; SLE, Dermatomyositis; DM, Systemic sclerosis; SSc), AA, malignant skin tumor, eczema in the order (Figure 6). The number and prevalence of hyperhidrosis patients in each disease were as follows. Psoriasis; 35 patients (17.7%), AD; 26 patients (13.1%), collagen disease; 25 patients (12.6%), AA; 14 patients (7.1%), malignant skin tumor; 13 patients (6.6%), and eczema; 8 patients (4.0%). The diseases found in only one or two patients were classified as “others”. There are no significant differences in odds ratios for each disease and hyperhidrosis (Figure 7).

We performed individual statistics on inflammatory skin diseases such as psoriasis, AD, and AA, that were frequently associated with hyperhidrosis (Figure 6). The male-female ratio, and age of hyperhidrosis in each disease are summarized in Figures 8, 9. The number of patients and prevalence rates for hyperhidrosis by location (head and face, axillary, palmar and plantar) and total in AD, psoriasis, and AA were summarized in Table 2.

In AD, the male-to-female ratio was 1:1.17 among patients with hyperhidrosis and 1:0.55 among those without, indicating a tendency toward female predominance, although the difference was not statistically significant (P = 0.109) (Figure 8A). In psoriasis, the ratios were 1:0.52 and 1:0.56, respectively, showing no apparent sex difference (Figure 8B). In AA, the ratios were 1:1.8 and 1:1.4, respectively, with no significant difference observed (Figure 8C). Thus, a female predominance was noted in AD and AA, whereas psoriasis showed a balanced distribution between sexes.

The mean age of AD patients with hyperhidrosis (42.0 years, SD 15.5) did not differ from those without (42.3 years, SD 18.6) (Figure 9A). In psoriasis, patients with hyperhidrosis (51.6 years, SD 13.7) were significantly younger than those without (59.8 years, SD 16.5, p = 0.017) (Figure 9B). In AA, no significant age difference was found between patients with (43.7 years, SD 17.5) and without hyperhidrosis (39.9 years, SD 22.1) (Figure 9C).

In AD, the most frequently affected sites were the head and face (20.2%), followed by the axillae (7.9%), and the palmar and plantar (6.7%). A similar pattern was observed in psoriasis (head/face: 17.7%, axillae: 9.9%, palms/soles: 7.1%). In AA, the head and face were also the most commonly affected sites (20.0%); however, axillary involvement (16.0%) was relatively more frequent than in AD and psoriasis, followed by the palmar and plantar (8.0%) (Table 2). Therefore, the head and face represented the predominant site across all three diseases, while AA was characterized by a higher prevalence of axillary hyperhidrosis compared with AD and psoriasis.

In comparison among AD, psoriasis, and AA, the percentages of patients who reported HDSS 3 or higher were 50%, 65.7%, and 35.7% (Figure 10).