Cost‐of‐illness study for axillary hyperhidrosis in Japan

Abstract The prevalence of primary axillary hyperhidrosis in Japan is 5.75% (males, 6.60%; females, 4.72%) in the population aged 5–64 years. No study on comprehensively evaluated direct medical costs, hygiene product costs, and productivity loss in axillary hyperhidrosis patients has been published in Japan. The aim of this study was to estimate the cost of illness for axillary hyperhidrosis in Japan by conducting a nationwide insurance claims database analysis and a cross‐sectional Web‐based survey. Among patients diagnosed with primary axillary hyperhidrosis at least once between November 2012 and October 2019, health insurance receipt data of 1447 patients were analyzed. A cross‐sectional Web‐based survey was conducted on 321 patients aged 16–59 years with axillary hyperhidrosis to calculate hygiene product costs and productivity loss using a Work Productivity and Activity Impairment questionnaire. Furthermore, nationwide estimation was performed for the hygiene product costs and productivity loss based on the number of patients estimated from the prevalence. The annual direct medical costs per axillary hyperhidrosis patient were ¥91 491 in 2016, ¥93 155 in 2017, and ¥75 036 in 2018. In all of these years, botulinum toxin type A injection accounted for approximately 90% of the total costs. The annual total cost of hygiene products per axillary hyperhidrosis patient was ¥9325. The overall work impairment (%) of working patients with axillary hyperhidrosis was 30.52%, and its monthly productivity loss was ¥120 593/patient. The activity impairment (%) of full‐time housewives with axillary hyperhidrosis was 49.05% and its monthly productivity loss was ¥176 368/patient. The annual hygiene product cost based on the nationwide estimation was ¥24.5 billion and the monthly productivity loss was ¥312 billion. The significant cost associated with axillary hyperhidrosis was clarified. If out‐of‐pocket expenses for treatments not covered by health insurance are included in the estimation, the cost will further increase.


| INTRODUC TI ON
Primary axillary hyperhidrosis, a disease of unknown pathogenesis with no underlying disease, interferes with daily life because of excessive axillary sweating. It is primary focal hyperhidrosis classified as an intractable disease. A questionnaire survey conducted by Fujimoto et al. 1 in a Japanese population aged 5-64 years (5807 valid responses) revealed the prevalence of primary axillary hyperhidrosis to be 5.75% (6.60% and 4.72% in males and females, respectively) between December 2009 and January 2010. The distribution of Hyperhidrosis Disease Severity Scale (HDSS) scores of 1, 2, and 3 or 4 (severe) was 5.6%, 47.6%, and 46.8%, respectively, suggesting that nearly half of the respondents had severe symptoms.
Cost-of-illness studies aim to identify and measure all of the costs of a particular disease, including the direct, indirect, and intangible dimensions. Direct costs consist of health-care costs and non-health-care costs like for transportation and household expenditure. Indirect cost generally refers to lost productivity resulting from morbidity or mortality in pharmacoeconomics and outcomes research area. Intangible cost is the costs assigned to the amount of suffering that occurs because of the disease or health-care intervention. 2 It is widely believed that estimating the total societal cost of an illness is a useful aid to policy making, and organizations such as the World Bank and the World Health Organization commonly use such studies. [3][4][5][6] Many cost-of-illness studies targeted for various countries have been reported in the field of dermatology. [7][8][9][10] Axillary hyperhidrosis causes psychological burdens, such as depression, loss of self-confidence, and weakness, 11 suggesting significant emotional burdens. Moreover, a Work Productivity and Activity Impairment (WPAI) survey of hyperhidrosis patients who visited a university hospital demonstrated the presenteeism of hyperhidrosis patients to be 47.14%, suggesting the significant effects of hyperhidrosis on work performance. The productivity loss associated with hyperhidrosis in Japan in 2009 was estimated to be ¥197 billion/month. 12 As axillary hyperhidrosis is treated at one's own expense and by health insurance, only limited information is available on treatment methods and medical costs. Furthermore, little information is available on the costs of so-called self-medication, namely hygiene products such as sweat pads and antiperspirants.
The aim of this study was to estimate the cost associated with axillary hyperhidrosis in Japan by conducting a nationwide insurance claims database analysis and a cross-sectional Web-based survey.

| Study design
Direct medical costs, hygiene product costs, and productivity loss were estimated as a cost associated with axillary hyperhidrosis in Japan. Direct medical costs were estimated using a nationwide insurance claims database provided by JMDC. 13 Hygiene product costs and productivity loss were estimated using the results of the cross-sectional Web-based survey.

| Direct medical costs
Direct medical costs were estimated using the receipt data from 31 412 patients who made at least one visit for hyperhidrosis (the corresponding ICD-10, International Classification of Diseases, 10th Revision, and the name of illness are shown in Table 1

| Self-medication costs and productivity loss
Hygiene product costs and productivity loss in 321 patients aged 16-59 years with HDSS score 2 or above (adjusting HDSS 2:3:4 to approximately 1:1:1) who met the diagnostic criteria for primary axillary hyperhidrosis were estimated based on the cross-sectional Web-based survey conducted in April 2020.
Hygiene product costs were defined as annual costs for purchasing clothes/towels, sweat pads, antiperspirants (sprays, sheets, and creams), body cleansers (soap and body soap), foods, and supplements.
Using a WPAI survey questionnaire which is a well-validated instrument to measure impairments in work and activities, 14 productivity loss was determined as absenteeism (%), presenteeism (%), and overall work impairment (OWI) (%) in working patients with axillary hyperhidrosis and activity impairment (AI) (%) in full-time housewives with axillary hyperhidrosis. To calculate productivity loss in working patients with axillary hyperhidrosis, each score was multiplied by monthly wages by sex and age, 15 and converted into productivity loss (¥/month). To calculate productivity loss in full-time housewives with axillary hyperhidrosis, each score was multiplied by the monthly housework activity evaluation value 16 and converted into productivity loss (¥/month).
In general, to estimate productivity loss, annual costs are calculated on the assumption that such productivity loss based on a WPAI survey continues for 1 year. However, seasonal fluctuations in productivity loss should be considered in view of the characteristics of hyperhidrosis. Therefore, to avoid overestimation/underestimation due to the fluctuations, the estimation period was set as 1 month.

| Nationwide estimation
Nationwide estimations were performed on hygiene product costs and productivity loss in axillary hyperhidrosis patients with HDSS 2 or above.

Productivity loss for AI
The productivity loss (¥/month) per patient, corresponding to AI (%), by HDSS adjusted by age distribution was estimated by multiplying the productivity loss (¥/month) per patient by age and HDSS obtained in the Web-based survey by the age distribution of patients.
The resulting productivity loss was multiplied by the number of full-time housewives by HDSS to estimate the nationwide productivity loss (¥/month), corresponding to AI.

| Direct medical costs
The characteristics of the analysis population are summarized in

| Self-medication costs
The patient backgrounds revealed in the Web-based survey are summarized in Table 3. Females accounted for 60.1% of all and the age distribution peaked at 40s (43.9%). The most common status of employment was regular worker (33.6%), followed by temporary or part-time worker (27.1%).
The annual total cost of hygiene products per axillary hyperhidrosis patient was ¥9325 (Table 4). The highest cost (¥13 786) per purchaser was associated with foods and supplements. The annual total cost of hygiene products by sex and HDSS was ¥10 510 in males, being higher than the ¥8539 in females. Both males and females spent more at a higher HDSS level.

| Productivity losses
The OWI (%) in working patients with axillary hyperhidrosis was 30.52% (Table 5). It was 32.18% in females, being higher than the 29.03% in males. Both males and females had a slightly higher OWI (%) in regular workers (29.66% and 33.18%, respectively).
Presenteeism accounted for the majority of OWI. The AI (%) of full-time housewives with axillary hyperhidrosis was 49.05%.

| Nationwide estimation
Nationwide estimates in axillary hyperhidrosis patients with HDSS 2 or above are summarized in Table 6.
The annual hygiene product cost was ¥24.5 billion (¥15 and ¥9.5 billion in males and females, respectively

Items HDSS n
Annual hygiene product cost (¥/patient)

Mean SD Median
Overall

| DISCUSS ION
In the present study, the cost associated with axillary hyperhidrosis in Japan was estimated by conducting a nationwide insurance claims database analysis for direct medical costs, and a cross-sectional Web-based survey for hygiene product costs and productivity loss.
As a result, the direct medical cost required for axillary hyperhidrosis was estimated to be ¥75 036/year (FY 2018) per patient.
The use of botulinum toxin type A injection is limited for only severe cases of primary axillary hyperhidrosis under universal health insurance coverage in Japan. Health insurance-covered treatment using botulinum toxin type A injection accounts for only 20% (doctors in private practice) and 33% (doctors in public practice) in Japan. 21 Therefore, many patients visit a department of cosmetic dermatology at their own expense, suggesting that the actual medical costs are even higher.
The hygiene product cost per patient was ¥9325/year (¥10 510 and ¥8539/year in males and females, respectively), suggesting that males spend more than females. The cost slightly increased at a higher HDSS level. As productivity loss, the absenteeism (%) and presenteeism (%) of working patients with axillary hyperhidrosis were 0.49% and 30.03%, respectively, suggesting approximately 30% decrease in work performance due to symptoms. The performance was slightly lower in patients with HDSS 3-4 than in those with HDSS 2. Based on these results, the annual hygiene product cost for axillary hyperhidrosis was estimated to be ¥24.5 billion, and Abbreviations: ; AI, activity impairment; HDSS, Hyperhidrosis Disease Severity Scale; OWI, overall work impairment; SD, standard deviation; WPAI, Work Productivity and Activity Impairment.
WPAI Questionnaire: Q1. During the past 7 days, how many hours did you miss from work because of problems associated with your underarm sweating?
Q2. During the past 7 days, how many hours did you actually work?
Q3. During the past 7 days, how much did your underarm sweating affect your productivity while you were working? (Answered on a 0-10 score, with 0 = underarm sweating had no effect on my work and 10 = underarm sweating completely prevented me from working.) Q4. During the past 7 days, how much did your underarm sweating affect your ability to perform your normal daily activities, other than work at a job? (Answered on a 0-10 score, with 0 = underarm sweating had no effect on my daily activities  The cost associated with primary axillary hyperhidrosis in Japan was clarified. Active interventions are needed for hyperhidrosis patients because improving the symptoms should reduce the societal loss by increasing productivity and improve the individual's quality of life. As estimated in our survey, the direct medical cost per patient with axillary hyperhidrosis in Japan was ¥75 036/year (FY 2018), the annual hygiene product cost was ¥24.5 billion, and the societal loss associated with the productivity loss was ¥312 billion/month. The hygiene product cost and the productivity loss slightly increased at a higher HDSS level. Considering the out-of-pocket expenses for treatments not covered by health insurance, the cost associated with axillary hyperhidrosis is even higher.

ACK N OWLED G M ENT
This study was funded by Kaken Pharmaceutical.