Dear Editor:
Atopic dermatitis (AD) is a common inflammatory skin disease that affects 10%~20% of children and 1%~3% of adults1,2. AD substantially affects patients’ quality of life and is a significant skin health-related global burden3,4. Understanding the prevalence and hospital utilization of AD across different age groups is essential for healthcare planning and patient counseling; however, data generalizable to the South Korean population are sparse. Furthermore, no study has investigated the treatment patterns of AD in Korea. Thus, we aimed to estimate the age-stratified prevalence of hospital utilization among patients with AD and investigate the medications prescribed for AD among pediatric and adult patients in a real-world clinical setting of South Korea.
We conducted a retrospective analysis using the Health Insurance Review and Assessment Service (HIRA) database of Korea from 2017 to 2019. We identified patients who had ≥1 AD diagnosis (using the International Classification of Diseases [ICD]-10 code L20.x as the primary diagnosis) annually, irrespective of history of previous AD. To assess hospital utilization attributable to AD, we estimated the 1-year prevalence of hospital-diagnosed AD, AD with ≥1 any AD medication, and AD with ≥1 moderate-to-severe AD medication, which were stratified by five age groups (infants, 0~1 year; pre-school children, 2~5 years; school-age children, 6~18 years; adults, 19~59 years; elderly adults, ≥60 years). AD-related medications include topical corticosteroids (TCSs), topical calcineurin inhibitors (TCIs), systemic corticosteroids (SCSs), immunosuppressants (cyclosporine, methotrexate, azathioprine, mycophenolate mofetil, and interferon-γ), intravenous immunoglobulin (IVIG), alitretinoin, phototherapy, antihistamines, and montelukast. Moderate-to-severe AD medication was defined as receiving at least one immunosuppressant, IVIG, alitretinoin, or phototherapy. The mid-year population of all age groups obtained from the Korean Statistical Information Service (KOSIS) served as denominators for the prevalence calculation (http://kosis.kr).
To investigate the prescribed medications for AD in Korea, we estimated the prevalence of six typical AD medication classes (TCS, TCI, SCS, cyclosporine, methotrexate, and other immunosuppressants). The medication prescribed was examined in the pediatric (<18 years of age) and adult (≥18 years) populations separately and stratified by medical institution type (primary versus secondary/tertiary hospital). Statistical analysis was performed using SAS version 9.4 (SAS Institute Inc.). This study was approved by the Institutional Review Board of Sungkyunkwan University, South Korea (SKKU 2020-09-009).
The overall prevalence of hospital-diagnosed AD in 2019 was 2.96% (n=1,593,009), and that of AD with ≥1 of any AD medication was 2.62% (Table 1). The prevalence of AD decreased with age: 24.19%, 12.24%, 5.80%, 2.04%, and 1.60% in the 0~1, 2~5, 6~18, 19~59, and ≥60 years, respectively. The prevalence of AD with ≥1 moderate-to-severe AD medication in 2019 was 0.10%, and the prevalence was highest in the 6- to 18-year-old group (0.19%).
Table 1. Prevalence of atopic dermatitis (AD), AD with ≥1 any AD medication, and AD with ≥1 moderate-to-severe AD medication* between 2017 and 2019, stratified by age group†.
| 2017 | 2018 | 2019 | |||
|---|---|---|---|---|---|
| Patients diagnosed with AD | |||||
| Age group (years) | |||||
| 0~1 | 187,075 (23.52) | 164,099 (22.87) | 157,887 (24.19) | ||
| 2~5 | 227,790 (12.46) | 212,924 (12.00) | 207,665 (12.24) | ||
| 6~18 | 373,606 (5.66) | 365,507 (5.66) | 364,978 (5.80) | ||
| 19~59 | 569,328 (1.79) | 592,765 (1.88) | 641,460 (2.04) | ||
| ≥60 | 197,173 (1.59) | 209,012 (1.60) | 221,019 (1.60) | ||
| Total | 1,554,972 (2.91) | 1,544,307 (2.88) | 1,593,009 (2.96) | ||
| Patients with ≥1 any AD medication | |||||
| Age group (years) | |||||
| 0~1 | 167,336 (21.04) | 145,395 (20.27) | 136,031 (20.84) | ||
| 2~5 | 210,213 (11.50) | 194,808 (10.98) | 186,695 (11.00) | ||
| 6~18 | 342,764 (5.19) | 333,945 (5.17) | 329,887 (5.24) | ||
| 19~59 | 511,524 (1.61) | 530,018 (1.68) | 565,241 (1.80) | ||
| ≥60 | 174,032 (1.41) | 184,794 (1.41) | 194,910 (1.41) | ||
| Total | 1,405,869 (2.63) | 1,388,960 (2.59) | 1,412,764 (2.62) | ||
| Patients with ≥1 moderate-to-severe AD medication | |||||
| Age group (years) | |||||
| 0~1 | 367 (0.05) | 373 (0.05) | 382 (0.06) | ||
| 2~5 | 1,344 (0.07) | 1,428 (0.08) | 1,538 (0.09) | ||
| 6~18 | 10,578 (0.16) | 11,100 (0.17) | 11,769 (0.19) | ||
| 19~59 | 26,605 (0.08) | 30,593 (0.10) | 35,511 (0.11) | ||
| ≥60 | 5,366 (0.04) | 6,178 (0.05) | 7,197 (0.05) | ||
| Total | 44,260 (0.08) | 49,672 (0.09) | 56,397 (0.10) | ||
Values are presented as number (%). *Moderate-to-severe AD medication was defined as receiving at least one immunosuppressant (cyclosporine, azathioprine, methotrexate, mycophenolate mofetil, and interferon-γ), intravenous immunoglobulin, alitretinoin, or phototherapy. †The mid-year population of all age groups obtained from the Korean Statistical Information Service (KOSIS) served as denominators for the prevalence calculation.
TCS was the most prescribed medication for AD in both pediatric and adult cohorts, ranging from 60.0% to 91.0% (Fig. 1). All individual medication classes, except for TCS, were prescribed more in adults than in pediatrics. TCIs and immunosuppressants were used more in secondary/tertiary care than in primary care, whereas SCSs were used more in primary care (pediatrics: 32.4% vs. 17.0%; adults: 58.5% vs. 37.2% in 2019).
Fig. 1. Prevalence of individual medication prescribed for atopic dermatitis in the pediatric (A) and adult population (B), stratified by the hospital level. *Prevalence (%) was calculated by dividing the number of patients receiving each medication class by the total number of patients with atopic dermatitis who received ≥1 AD medication for each medical institution type by year.
A previous study using data from the Korean National Health and Nutrition Examination Survey (KNHANES) showed that the lifetime prevalence of AD was 5.9%, 11.3%, and 14.6% in infants, pre-school children, and school-aged children, respectively from 2016 to 20175; in comparison, they were 24.2%, 12.2%, and 5.8% in the present study. The lower prevalence of AD in infants and higher prevalence in school-aged children in KNHANES than in our study may be because the survey collects history of AD and may be susceptible to recall bias (especially for the events that occurred in infancy). Moreover, direct comparison is challenging, as the previous study estimated lifetime prevalence of AD and this study considers 1-year prevalence.
TCSs are first-line therapeutic agents against AD, as they usually bear little risk6,7. Consequently, most Korean patients with AD received TCSs to treat AD (approximately 90% of pediatric patients and 75% of adults). Immunosuppressants, used for moderate-to-severe AD, were prescribed more in secondary/tertiary care than in primary care, and cyclosporine was the most used immunosuppressant. Meanwhile, SCSs were used more frequently in primary care (around 30% of pediatrics and 60% of adults) than in secondary/tertiary care, although SCSs are generally recommended in exceptional cases for short-term flare treatment and are associated with multiple adverse events8. Previous studies in other countries also reported a high prevalence of SCS use among patients with AD; however, SCS use in Korea seems to be higher than that in other countries, especially in adults. In Denmark and Japan, approximately 12% and 30% of adults with AD received SCSs, respectively, whereas approximately 60% in Korea do9,10.
This study used the nationwide claims database covering the entire Korean population, thereby allowing the estimates to represent the country’s population. Nonetheless, our study has several limitations. The validity of the AD diagnosis in the claims data remains unclear because no study has validated the diagnostic code. This means that the diagnoses used in our study may not perfectly reflect actual disease. Additionally, it is likely to include prescriptions for conditions other than AD. However, to minimize this issue, we included only prescriptions corresponding to the primary diagnosis of AD. Lastly, we only presented general patterns of prescribed medications in pediatric and adult AD populations; still, we did not consider each patient’s specific age, symptoms, and clinical situations in detail.
In conclusion, based on the nationwide claims database of South Korea, a large number of patients with AD consistently visit hospitals and receive treatment across all age groups. The prevalence of hospital utilization varied by age group, from 1.6% for the elderly to 24.2% for infants. Although SCSs are not recommended as the primary therapy for AD, they are frequently prescribed to patients with AD, especially in primary care and the adult population. These results provide improved knowledge of hospital utilization and medications prescribed among the AD population and suggest the need to develop tailored strategies to treat AD and acceptance for safer and more effective systemic treatments.
Footnotes
CONFLICTS OF INTEREST: J.Y.J. and H.J.Y. are the employees and shareholders of Pfizer Inc. J.Y.S. received grants from the Ministry of Food and Drug Safety, the Ministry of Health and Welfare, the National Research Foundation of Korea, the Government-wide R&D Fund for Infectious Disease Research, and pharmaceutical companies, including Daiichi Sankyo, GSK, and Pfizer, outside the submitted work.
FUNDING SOURCE: This study was supported by Pfizer Pharmaceuticals, Korea, Ltd.
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