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Analysis of Healthcare Utilization for Primary Dysmenorrhea in Korea: A Retrospective, Cross-Sectional Study

Purpose This study is a retrospective, cross-sectional study aiming to present basic data on the treatment modalities and cost of care for primary dysmenorrhea (PD) by analyzing healthcare utilization and patient distributions using the 2010 to 2018 Health Insurance Review and Assessment Service (HIRA) data. Patients and Methods We used the HIRA-National Patient Sample (NPS) data to analyze medical service utilization for PD (ICD-10 code: N94.4, N94.6) in Western medicine (WM) or Korean medicine (KM) care between January 2010 and December 2018. Results There were 41,139 patients diagnosed with PD who utilized Western medicine (WM) or Korean medicine (KM) care at least once during the study period. The number of claims and patients steadily rose over the years from 7430 claims for 3989 patients in 2010 to 11,523 claims for 6226 patients in 2018. The predominant age group was 15 to 24 years. Regarding the frequency of service categories for PD in the claims, consultation was the most common and costly service category in WM (72,120 cases, 47.89%; 631,912 USD, 69.74%), while injection and analogous treatments was the most common and costly service category in KM (97,157 cases, 72.41%; 314,696 USD, 55.86%). Regarding the drug prescriptions, nonsteroidal anti-inflammatory drugs (NSAIDs) (26,617 cases, 40.47%) were the most frequently prescribed drug for PD in pharmacies and hospitals. Conclusion The result shows an annual increase in healthcare utilization for PD with the fastest rate in individuals aged 15 to 24 years. This study provides data on the current utilization of WM and KM care for PD for policymakers. Furthermore, we analyzed the frequency and cost of common treatment modalities in WM and KM, which would be useful data for clinicians and researchers.


Introduction
Primary dysmenorrhea (PD) is defined as periodic cramps and pain originating from the uterus during the menstrual period, and it is the most common gynecological disease among women of reproductive age. 1 PD is not linked to a clear pathological pelvic disease and tends to first occur in women aged 20 years or younger after the ovulation cycle. Pain occurs within a few hours of the menstrual bleeding and peaks on the first or second day. 2 Intense pain is limited to a specific lower abdominal quadrant and radiates to the inner thigh. 3 PD is generally diagnosed based on the presence of pain and elimination of abnormal signs in the pelvic cavity based on history taking and examination. 4 The prevalence of PD varied widely across previous studies. It ranged from 16 to 91% among women of reproductive age, with 2 to 29% suffering from extremely severe pain. 5 According to a study that analyzed research conducted on adolescents and young women (≤ 30 years) worldwide, 34 to 94% of the women suffer from dysmenorrhea. 6 Furthermore, one study reported that the prevalence can range from 15 to 75% because of the heterogeneity in the study criteria and population. 7 The prevalence is 87-90% among Korean women, and 10-25.6% have reported severe symptoms. 8 Despite the markedly high prevalence, women with PD tend to engage in self-treatment. 9 While the general treatment goals of PD are reported to be symptom improvement and reduction of work-loss or school-loss days, 10 the majority of female students who suffer from PD only took over-the-counter drugs or tried nonpharmacological remedies, and did not frequently receive professional medical care at healthcare facilities.
Western Medicine (WM) treatments for PD can be broadly divided into pharmacological and nonpharmacological treatments. 10 Studies generally report that treatments involving nonsteroidal anti-inflammatory drugs (NSAIDs) 11 or hormonal contraceptives 12 to reduce prostaglandins and leukotrienes are effective. 13 Furthermore, several studies evaluated lifestyle changes, 14 nonpharmacological treatments and complementary and alternative medicine (CAM) treatments for PD, 15 including nutritional method, exercises, and Korean Medicine (KM). 10,16 CAM treatments can be chosen as medical interventions to prevent or alleviate PD. 17 Recent studies introduced several CAM treatment modalities for PD, including acupuncture, acupressure, moxibustion, 18,19 muscle relaxation, 20 nutritional functional foods, 21 and aromatherapy. [22][23][24] A study suggested that acupuncture can more effectively reduce PD and relevant symptoms compared to NSAIDs and that the therapeutic effects are retained in the short term. 25 According to Akiyama's five-year study utilizing the Japan Health Insurance (JMDC) database from 2009, 26 patients had approximately one day of therapy (DOT) for every 45 days due to dysmenorrhea (ICD-10 code N94.4, N94.6). The average total cost of health management per year was about 2.2 times greater in PD group, and the excess cost was generally incurred by outpatient care. The annual pharmacy cost was also about 2.6 times higher in the PD group than in the control group. Furthermore, PD has a strong impact on patients' lives. According to a Japanese study, 27 27.3% of women missed school or work at least one day in six months, and 50% of women with PD in Sweden have been absent to work or school at least once due to menstrual pain, which is approximately 230,000 work loss days. 1 Statistics on the disease codes that comprise PD (ICD-10 code N94.4 and N94.6) from the 2018 National Health Insurance Statistical Yearbook of Korea 28 show that 236,558 patients utilized outpatient healthcare service with the reimbursed cost of care totaling 10.3 billion KRW, showing that the NHI spending for PD is not low.
Previous studies specifically analyzed the prevalence of PD by age and country and observed that there is substantial consequent economic loss. Moreover, many studies assessed the general treatment modalities used for PD and their effectiveness. 21,[29][30][31] However, studies that investigate the overall healthcare utilization for PD and the specific cost of each service are lacking. While studies conducted in Japan 26 and Taiwan 32 reported healthcare utilization for PD and secondary dysmenorrhea, there is insufficient research data, necessitating national-level epidemiology studies to investigate the cost of healthcare utilization and types of treatments.
Based on the insufficient evidence from previous studies and the importance to examine the prevalence and treatments of PD for appropriate guidelines, this study was conducted under the aim to present the clinical treatment trends for PD and examine the changes in healthcare utilization.

Study Design Data Source
This study was a retrospective, cross-sectional, descriptive study used the Health Insurance Review and Assessment Service-National Patient Sample (HIRA-NPS) data from January 2010 to December 2018. The data are massive and cover 460 million patients annually, which accounts for 90% of the Korean population, under the NHI system. As of 2011, the data comprise claims received from approximately 80,000 healthcare providers nationwide. 33 The NPS data include claims received for a randomly selected 3% of the entire Korean population (about 1.4 million as of 2018) stratified by sex (2 strata) and age (16 strata). This is secondary data statistically sampled from the raw data after de-identification and contains claims submitted each year from the date of initial care for the corresponding year. It is generated when healthcare providers submit their claims for reimbursement of the cost of care to the National Health Insurance Service (NHIS), and it is highly useful for healthcare research owing to the detailed and diverse types of information (details of care [eg, treatment, medical procedure, diagnostic test, prescription], diagnosis, the amount paid by the insurer, patient's out-of-pocket cost, patient demographics, and information about care facility).

Study Population
In this study, we included patients who received WM or KM care at least once with ICD-10 code N94.4 (primary dysmenorrhea) or N94.6 (dysmenorrhea, unspecified) as the main diagnosis between 2010 and 2018. 26 Among the claims submitted with KCD code N94.4 or N94.6, those with codes for the dental institution, public health facility, or psychiatry, institution types as nursing hospital, psychiatric long-term care hospital, dental hospital, maternity facility, or public health facility, and total cost of care or number of days in care entered as 0 or missing were excluded.

Study Outcomes
To analyze the frequency and percentage of utilization of WM and KM institutions, the selected patients were classified by age and payer type. Age was divided into six 10-year age groups from < 15 years to ≥ 55 years, and payer type was categorized into NHI and Medicaid. Except for the people in the lowest income level, which is subsidized by taxes and covered by Medicaid, all Koreans are forced to take part in national health insurance. Thus, NHI and Medicaid are representative of the patient's household economic status. Age was further divided based on time to visualize the number of people utilizing healthcare per year using graphs. The type of visit was categorized into outpatient and inpatient, and the medical institution was classified into tertiary hospital/general hospital/hospital, clinic, KM hospital, and KM clinic. The total number of patients utilizing each medical institution and average visits per patient for each year were graphed. The specific results for the number of patients, total claims, total costs, per-patient costs, and per-claim costs were also analyzed.
According to the Ministry of Health and Welfare (MOHW) criteria, service categories were classified into injection and analogous treatments, consultation, testing, medication administration, inpatient care, procedure and surgery, other, special equipment, and diagnostic imaging. The annual average number of cases, annual growth rate of cases, annual average cost, and annual growth rate of cost and the results for five practices (service codes) in the KM claims are evaluated.
Medications were categorized according to the Anatomical Therapeutic Chemical Classification System-code (ATC code) of each drug according to the MOHW criteria, and the total number of prescriptions and costs, as well as the annual average number of prescriptions, growth rate of prescriptions, average total cost, and growth rate of the total cost, were assessed for each category (Supplementary Table 1).
In this study, all costs are the cost spent by a health insurance subscriber at a healthcare institution, and it is the allowed cost (sum of NHIS payment and patient's out-of-pocket cost) from the total cost claimed by a medical institution.

Statistical Analysis
Based on the objective of the study and the imbalance of the size of the two (WM and KM) groups, this study employed a descriptive approach instead of a direct statistical comparison of the two groups. The basic characteristics of the patients are presented as the number of patients and percentage. The frequency and costs of each service category and prescription category were analyzed. Types of healthcare services were defined to analyze the frequency and total costs. All prescribed medicines were categorized by ATC codes. The average annual log change (as growth rate) of each category were investigated. All cost values were converted to USD based on the 2018 average KRW to USD exchange rate and adjusted using the price index of healthcare cost of the corresponding year (Supplementary Table 2). The data were analyzed using SAS software (version 9.4, SAS Institute, Cary, NC, USA).

Basic Characteristics of Patients and Medical Claims
The predominant age group utilizing medical institutions in Korea (WM and KM) with PD as the main diagnosis was 15 to 24 years (n=19,201, 46.67%), followed by 25 to 34 years (n=11,535, 28.04%) and 35 Figure 2). Regarding the type of visit, 99.69% of the claims were for outpatient care, and 0.31% were for inpatient care. Regarding the type of medical institution in WM, 64.37% were from a primary health care facility (clinic level), and 35.62% were from a tertiary hospital/general hospital/hospital, but in KM, 95.82% of the claims were from a primary health care facility, showing a higher utilization of primary healthcare facilities compared to that in WM (Supplementary Table 3).

General Medical Usage for Patients in Korea
The total number of patients that sought healthcare (WM and KM) in Korea rose by 55.34% from 4060 in 2010 to 6307 in 2018. Moreover, the total number of claims also rose by 55.09% from 7430 claims in 2010 to 11,523 claims in 2018, and total cost increased by 115.93% from 116,254 USD in 2010 to 251,032 USD in 2018 (Supplementary  Table 4). However, the annual average visits per patient remained steady over the years at 1.5 in WM and 3.5 in KM (Figure 3).
The service codes for KM practices were categorized into five categories, and frequencies were analyzed for the nine-year period. Acupuncture was most commonly performed (54,269 cases), followed by moxibustion (13,775 cases) and heat-cold meridian therapy (11,696 cases). Furthermore, acupuncture incurred the highest cost (204,594 USD), followed by     Table 6).

Frequently Prescribed Medicine for Primary Dysmenorrhea
In KM, packaged medicinal herbs are most frequently prescribed, but because it is not covered by the NHIS, prescriptions were excluded from the analysis. We analyzed all prescribed drugs in WM without differentiating whether it was filled at a pharmacy or hospital. The most frequently prescribed drug was NSAIDs (26,617 cases), followed by drugs for functional gastrointestinal disorders (13,225 cases) and drugs for acid-related disorders (9034 cases). The drug associated with the highest cost was sex hormones and modulators of the genital system (51,640.05 USD), followed by NSAIDs (38,743.74 USD) and drugs for functional gastrointestinal disorders (18,492.71 USD) ( Table 3).

Discussion
This study analyzed the characteristics of patients with PD, treatment modalities, cost of care, and annual distributions using the HIRA-NPS data from 2010 to 2018. The most common age group diagnosed with PD was 15 to 24 years (n=19,201, 46.67%), and healthcare utilization for PD in this age group doubled during this period. The number of patients seeking healthcare (including WM and KM) for PD steadily rose over the years, and it has rapidly increased since 2015. Aside from consultation, testing was the most frequently billed service category in WM, while injection and analogous treatments were the most frequently billed service category in KM. NSAIDs were the most frequently prescribed drugs for PD.
Of the 3% random sample from the entire Korean population, 4571 individuals (41,139 for nine years) utilized healthcare for PD every year, which accounts for 0.331% of the 1.4 million sample population (Figure 1). Compared to the prevalence of PD among female college students reported in a Chinese cross-sectional study (41.7%) 34 and that reported in a Spanish cross-sectional study (76%), 35 the rate of healthcare utilization by Koreans was low compared to the prevalence, even after considering that the number of people who sought healthcare may be slightly larger because we only analyzed health insurance claims data. The reason that women suffering from PD rarely seek healthcare has been examined in a previous online survey study. 36 Furthermore, considering that patients tend to take a symptomatic approach to treat PD using over-The-counter drugs, as opposed to seeking professional healthcare, 37 this may suggest that the percentage of patients with PD requiring medical intervention or the awareness of treatment options is low. Moreover, the results imply that patients manage their PD through conservative treatment or self-care measures such as aerobics or exercise. [38][39][40] Our results are consistent with that of a study on Canadian women with PD that these women are likely to resort to non-prescribed treatments, as opposed to prescribed drugs, for pain relief. 41 The results of this study show that healthcare utilization for PD in Korea is gradually on the rise in recent years. Considering that the per-patient average number of visits remained steady, the increase in healthcare utilization can be attributable to an actual increase in healthcare utilization by a greater number of patients and not due to unnecessary healthcare. Specifically, Figure 2 shows that the number of claims from obstetrics and gynecology (OB/GYN) for patients aged 15 to 24 years and the number of patients in this age group dramatically rose from around 2016. This shows that there have been many changes in the utilization of OB/GYN care among single women since the publication of a 2014 study by the Korea Institute for Health and Social Affairs on the need to change the perception of single women who avoid utilizing OB/GYN care. There has been an effort to transform the perception about OB/GYN care in Korean society, as evident by the major policy changes to expand health insurance coverage to human papillomavirus (HPV) vaccine 42 and a 2015 grounded theory study identifying the negative social perception about single women visiting OB/GYN. 43 However, more detailed policy studies are needed to determine whether the health insurance coverage and study attempting to change perception have directly contributed to the increased OB/GYN utilization. An example is the increased healthcare utilization by the older adult population after changes in policies, such as lowering out-of-pocket costs and raising the upper limit of a fixed out-of-pocket cost system for adults aged 65 years or older in Korea. 44 In WM, testing incurred the highest cost, followed by medication administration, injection and analogous treatments, hospitalization, treatment, and surgery. In KM, injection and analogous treatments incurred the highest cost, followed by medication administration, hospitalization, and others. Moreover, we further divided Korean treatments into five service codes (Supplementary Table 6) and observed that acupuncture incurred the highest cost, followed by moxibustion and cupping therapy. In contrast, in WM, testing, including general laboratory tests, urine microscopes, and electrolyte tests, incurred the highest cost. In practice, PD is differentiated from secondary dysmenorrhea through the laboratory. 45 Laboratory testing is considered essential to the diagnosis of dysmenorrhea, which is speculated to be the reason for the high percentage of cost spent on this service category. After differential diagnosis, PD is traditionally treated through pharmacologic therapeutic options. Surgical treatment is not supported by sufficient evidence 46 and is recommended as the last resort, 47 which may be the reason for the low percentage of "other" service categories.
Service codes related to physiotherapy are not shown in our statistical data, presumably because OB/GYN clinics often lack physiotherapy-related facilities and equipment due to the nature of diseases. Past studies suggested that physiotherapy modalities such as transcutaneous electrical nerve stimulation (TENS) 48,49 or kinesio taping can improve pain associated with PD and enhance patients' quality of life. A Japanese study 50 also reported that patients tend to prefer alternative medicine to treat PD due to the effectiveness of nonpharmacologic therapeutic options and patients' perception. 3,9,36,51 However, we can speculate that the total number of claims and cost were highest for acupuncture in KM 52 because acupuncture and cupping therapy are covered by insurance and are employed as the main treatment modalities. 53 Similarly, moxibustion and cupping therapy are often coupled with acupuncture in KM, which explains their high percentages in the cost analysis for different service codes. Past studies have reported that acupuncture is significantly effective in treating PD 24,25,54 and suggested that moxibustion may also be effective. 19,[55][56][57] The Korean government launched a pilot project for expanding NHI coverage to packaged medicinal herbs in November 2020 for certain diseases with high health insurance coverage needs, including PD. 58 As the demands for KM care are expected to rise among patients with PD as a result of the pilot project, we expect many relevant studies to be conducted in the coming years.

1023
As shown in Table 3, the most frequently prescribed drug for PD in all WM institutions is NSAIDs, followed by drugs for functional gastrointestinal and acid-related disorders. NSAIDs are widely used to relieve acute or chronic pain, 59,60 and foreign study findings show that NSAIDs are effective on PD. [61][62][63] Foreign guidelines that recommend the priority use of NSAIDs in treating PD 47 are consistent with our prescription frequency results. Moreover, we can speculate that drugs for functional gastrointestinal and acid-related disorders are also frequently prescribed 64,65 to resolve the gastrointestinal side effect induced by NSAIDs. 66,67 The findings of this study on the current trend of healthcare utilization by patients with PD are nationally representative. Moreover, this is the first study to analyze WM and KM care for PD in reflection of the unique dichotomized healthcare system in Korea. We shed light on basic trends of the medical cost and treatment frequencies for PD using the national HIRA-NPS data that encompass all age groups and regions. Hence, the findings will be useful for further research on WM and KM care for PD.
This study has a few limitations. First, while the data contain information about healthcare utilization for PD in the corresponding years, it is difficult to conclude that the patients received treatments listed in the claims solely for PD. According to a previous study, 68 the diagnostic accuracy of health insurance claims data is approximately 70. To address this, we only included those with PD as the main diagnosis; however, we could not isolate treatments for PD and those for other diseases. Second, the study data are not a continuous but annually repeated and cross-sectional. Cohort studies will be needed if patients with PD need follow-up in the long term. Third, we could not analyze the clinical manifestations and severity of PD. Additional studies are needed to examine healthcare utilization according to its clinical symptoms. Fourth, the claims data only contained 201 service categories for KM, which is substantially fewer than 5611 service categories in WM, showing that many KM service categories are not covered by health insurance.

Conclusions
This study examined the trends of healthcare utilization for PD (types and cost of treatment for PD) in Korea using the HIRA-NPS data. We observed that it is low compared to its prevalence and that healthcare utilization for PD is increasing in Korea over the years in contrast to foreign reports that patients tend to prefer home remedies and self-care for PD. The total cost of care also increased. In WM, the cost for consultation and testing accounted for the greatest percentage, while in KM, injection and analogous treatments (acupuncture followed by moxibustion and hot-cold meridian therapy) and consultation incurred the highest cost. Considering that not many studies have analyzed the trends of healthcare utilization for PD at the national level, this study that encompassed WM and KM care provides valuable information about PD for professionals such as health policymakers, clinicians, and researchers, and the findings would be useful as foundational data for relevant pilot projects and policy decision making.

Data Sharing Statement
Patient Samples can be obtained via the website of HIRA by filling out the End User Agreement of the Patient Samples. The Patient Samples are provided in a DVD (text file) format and a fee for the samples is subject to be charged. https://opendata.hira.or.kr/home.do.

Ethics Approval and Informed Consent
This study protocol was approved by the public data provision deliberation committee in the HIRA and conducted according to relevant guidelines and regulations. It was reviewed and qualified as an exemption by the Institutional Review Board of Jaseng Hospital of Korean Medicine, Seoul, Korea (2021-05-002). All study participants provided https://doi.org/10.2147/IJWH.S366386

DovePress
International Journal of Women's Health 2022:14 informed consent, and the study design was approved by the appropriate ethics review board. The principles expressed in the Declaration of Helsinki have been adhered to in the analysis.

Author Contributions
All authors made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; took part in drafting the work or revising it critically for important intellectual content; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding
This study was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health and Welfare, Republic of Korea (HF20C0222). The funders had no role in developing the protocol.

Disclosure
The authors declare no conflicts of interest.