Introduction

The annual number of outpatient visits in Japan is 12.4 per capita, which is relatively high compared to other Organization for Economic Co-operation and Development (OECD) countries [1]. Japan has a universal health insurance system for its population and within the framework of this system, the country has meticulously established a reimbursement system for high-cost medical care, and exemptions for individuals with limited income, which allows the public free access to medical care, both as policy and in practice. However, the frequency of outpatient visits reportedly decreased during the COVID-19 pandemic due to fear of getting infected [2]. Therefore, this study aimed to determine the change in the number of outpatient visits in Japan since the beginning of the COVID-19 pandemic using a comprehensive administrative database containing data of almost 100 million Japanese residents.

Methods

The data were obtained from the National Database (NDB) of Health Insurance Claims and Specific Health Check-ups [3]. This database contains data collected using standardized health insurance claim forms used by medical facilities for claiming reimbursement from insurers. The insurance claims of almost all citizens are digitized in the same format, regardless of the insurer type [1]. The Ministry of Health, Welfare and Labor of Japan developed the NDB for planning, evaluating, and optimizing medical costs. The NDB data are available for analysis to a limited number of eligible applicants, including national administrative agencies, prefectures, universities, and national level medical insurers [4]. As of March 2019, 99.2% of hospitals, and 94.8% of clinics in Japan had digitized all health insurance claims, making research using data from the NDB more accessible across the nation [5].

Based on the outpatient claims submitted monthly by medical institutions to insurers in 2019 and 2020, we calculated the total number of outpatient visits, and number of visits for each disease according to the International Classification of Diseases-10 (ICD-10) codes on the claim form. The number of visits was converted to units per million population using the following formulae:

$$\begin{array}{l}{\rm{Visit\ rate\ per\ million\ population\ per\ year}} = \\{\rm{(total\ number\ of\ outpatient\ visits)}}\\\div {\rm{(total\ population\ based }}\\{\rm{on\ the\ Basic\ Resident\ Ledger\ in\ 2020)}} \times 365 \times {10^6}\end{array}$$
$$\begin{array}{l}{\rm{Visit\ rate\ per\ million\ population\ per\ year\ by\ disease }} = \\{\rm{(total\ number\ of\ outpatient\ visits\ for\ the\ disease)}}\\\div {\rm{(total\ population\ based }}\\{\rm{on\ the\ Basic\ Resident\ Ledger\ in\ 2020)}} \times 365 \times {10^6}\end{array}$$

If a patient received treatment for multiple diseases during a single visit, each treatment was counted as a visit for that particular disease. Diseases for which the number of outpatient visits increased from 2019 to 2020 received a negative score.

The difference in the number of visits in 2019 and 2020 was set as the denominator, and the difference in the number of visits for each disease in 2019 and 2020 was set as the numerator. From this, we calculated the percentage decrease in the visit rate per disease using the formula:

$$\begin{array}{l}{\rm{Percentage\ decrease\ in\ the }}\\{\rm{visit\ rate\ for\ the\ disease}}\\{\rm{ = 1 - (visit\ rate\ for\ the\ disease\ in\ 2020)}}\\\div {\rm{(visit\ rate\ for\ the\ disease\ in\ 2019)}} \times {\rm{100 }}\end{array}$$

This study complied with the provisions of the World Medical Association Declaration of Helsinki (as amended by the 59th General Assembly, Seoul, the Republic of Korea, October 2008), and was approved by the Ethical Review Committee of Nara Medical University (No.: 1123). The requirement for informed consent was waived as the data were anonymized.

Results

The number of outpatient visits per million people decreased by 9.98%, from 33,466 to 2019 to 30,127 in 2020. Of all the diseases included in the analysis, 71 showed a decrease in the number of visits by ≥ 1% (Table 1). There were significant decreases in the number of outpatient visits related to infectious diseases (such as influenza, viral infections of the skin, and mucous membranes, acute bronchitis, acute laryngitis, and acute upper respiratory tract infection), and chronic diseases (such as hemorrhoids, cystic kidney disease, dermatitis due to substances taken internally [ICD-10 code L27], dyspepsia, chronic sinusitis, and asthma).

Table 1 Diseases with significant decreases in outpatient visits
Full size table

Discussion

This study focused on the decline in outpatient visits during the COVID-19 epidemic. The observed decrease in the outpatient visit rate might have been due to a decrease in the incidence of disease, or a decreased frequency of visit by patients with the disease, or both. For instance, as genetic factors play a role in the development of some cancers, and cancers may develop over a period of years or decades, a certain percentage of the population will always be affected, regardless of the pandemic. The decrease in the visit rate for such diseases was probably due to an avoidance of medical consultations rather than a decrease in the disease incidence. On the other hand, for diseases that are strongly influenced by short-term changes in behavior, the decrease in the visit rate may have been either due to a decreased incidence of the disease, or an avoidance of medical consultations, or both. Previous studies have reported a decrease in the incidence of pediatric viral respiratory tract infections due to social distancing [4], and an absent seasonal influenza epidemic during the 2020–2021 influenza season across all age groups [5], demonstrating evidence of a decrease in the incidence of infectious diseases due to the pandemic. Access to medical care is likely to have become limited as a result of a combination of prioritization of care for COVID-19 patients, together with avoidance of consultation by patients for fear of contracting COVID-19. This could explain the reduction in the number of visits for chronic conditions. As this study analyzed data retrospectively, prospective studies can be designed to further validate our results.

As our dataset included more than 100 million people, and Japan has universal health insurance coverage, we were able to identify large-scale societal trends in medical consultations associated with the COVID-19 pandemic, such as a decrease in the incidence of infectious diseases other than COVID-19, a temporary limited access to medical facilities, and the avoidance of medical consultations.

Our analysis method using actual health insurance claim data can be applied not only in Japan but also in other countries where researchers have access to national information on health insurance claims [6,7,8]. As universal health coverage continues to be implemented in low- and middle-income countries, in keeping with World Health Organization recommendations, consideration should be given to developing health insurance databases also, which can be used for research purposes to draw-up health care policies not only for management of health crises such as the COVID-19 pandemic, but also for strengthening health care systems in general [9, 10].

Japan needs to consider ensuring that all patients have the right to receive necessary outpatient care during future pandemics and otherwise. In Japan, prior to the COVID-19 pandemic, telemedicine was covered by medical insurance only for very limited applications compared to other countries. For example, telemedicine was only allowed for re-consultation in underpopulated areas. During the COVID-19 epidemic in Japan, expansion of the use of telemedicine was actively discussed, and eventually initial telemedicine consultations for patients suspected of having COVID-19 in urban areas were included in the coverage by medical insurance on a limited basis [11]. We hope that Japan will review its policies with reference to reports regarding inclusion of medical insurance coverage of telemedicine consultations in other countries [12,13,14].

Limitations

This study was unable to determine whether decreased incidence of disease or decreased access to care predominated in causing the decrease in the number of outpatient visits during COVID-19 pandemic. The underlying cause is likely to have varied from disease to disease.