A Review of Studies Using Japanese Nationwide Administrative Claims Databases

Leveraging Administrative Health Databases to Address Health Challenges in Farming Populations: Scoping Review and Bibliometric Analysis (1975-2024)

BACKGROUND

Although agricultural health has gained importance, to date, much of the existing research relies on traditional epidemiological approaches that often face limitations related to sample size, geographic scope, temporal coverage, and the range of health events examined. To address these challenges, a complementary approach involves leveraging and reusing data beyond its original purpose. Administrative health databases (AHDs) are increasingly reused in population-based research and digital public health, especially for populations such as farmers, who face distinct environmental risks.

OBJECTIVE

We aimed to explore the reuse of AHDs in addressing health issues within farming populations by summarizing the current landscape of AHD-based research and identifying key areas of interest, research gaps, and unmet needs.

METHODS

We conducted a scoping review and bibliometric analysis using PubMed and Web of Science. Building upon previous reviews of AHD-based public health research, we conducted a comprehensive literature search using 72 terms related to the farming population and AHDs. To identify research hot spots, directions, and gaps, we used keyword frequency, co-occurrence, and thematic mapping. We also explored the bibliometric profile of the farming exposome by mapping keyword co-occurrences between environmental factors and health outcomes.

RESULTS

Between 1975 and April 2024, 296 publications across 118 journals, predominantly from high-income countries, were identified. Nearly one-third of these publications were associated with well-established cohorts, such as Agriculture and Cancer and Agricultural Health Study. The most frequently used AHDs included disease registers (158/296, 53.4%), electronic health records (124/296, 41.9%), insurance claims (106/296, 35.8%), population registers (95/296, 32.1%), and hospital discharge databases (41/296, 13.9%). Fifty (16.9%) of 296 studies involved >1 million participants. Although a broad range of exposure proxies were used, most studies (254/296, 85.8%) relied on broad proxies, which failed to capture the specifics of farming tasks. Research on the farming exposome remains underexplored, with a predominant focus on the specific external exposome, particularly pesticide exposure. A limited range of health events have been examined, primarily cancer, mortality, and injuries.

CONCLUSIONS

The increasing use of AHDs holds major potential to advance public health research within farming populations. However, substantial research gaps persist, particularly in low-income regions and among underrepresented farming subgroups, such as women, children, and contingent workers. Emerging issues, including exposure to per- and polyfluoroalkyl substances, biological agents, microbiome, microplastics, and climate change, warrant further research. Major gaps also persist in understanding various health conditions, including cardiovascular, reproductive, ocular, sleep-related, age-related, and autoimmune diseases. Addressing these overlooked areas is essential for comprehending the health risks faced by farming communities and guiding public health policies. Within this context, promoting AHD-based research, in conjunction with other digital data sources (eg, mobile health, social health data, and wearables) and artificial intelligence approaches, represents a promising avenue for future exploration.

Diagnostic validity and solute-corrected prevalence for hyponatremia and hypernatremia among 1 813 356 admissions

Background and hypothesis

We aimed to evaluate the diagnostic validity of the International Classification of Diseases, 10th Revision (ICD-10) codes for hyponatremia and hypernatremia, using a database containing laboratory data. We also aimed to clarify whether corrections for blood glucose, triglyceride, and total protein may affect the prevalence and the diagnostic validity.

Methods

We retrospectively identified admissions with laboratory values using a Japanese hospital-based database. We calculated the sensitivity, specificity, and positive/negative predictive values of recorded ICD-10-based diagnoses of hyponatremia (E87.1) and hypernatremia (E87.2), using serum sodium measurements during hospitalization (<135 and >145 mmol/l, respectively) as the reference standard. We also performed analyses with corrections of sodium concentrations for blood glucose, triglyceride, and total protein.

Results

We identified 1 813 356 hospitalizations, including 419 470 hyponatremic and 132 563 hypernatremic cases based on laboratory measurements, and 18 378 hyponatremic and 2950 hypernatremic cases based on ICD-10 codes. The sensitivity, specificity, positive predictive value, and negative predictive value of the ICD-10 codes were 4.1%, 99.9%, 92.5%, and 77.6%, respectively, for hyponatremia and 2.2%, >99.9%, 96.5%, and 92.8%, respectively, for hypernatremia. Corrections for blood glucose, triglyceride, and total protein did not largely alter diagnostic values, although prevalence changed especially after corrections for blood glucose and total protein.

Conclusions

The ICD-10 diagnostic codes showed low sensitivity, high specificity, and high positive predictive value for identifying hyponatremia and hypernatremia. Corrections for glucose or total protein did not affect diagnostic values but would be necessary for accurate prevalence calculation.

Clinical research using real-world data: A narrative review

Randomized controlled trials (RCTs) and studies using real-world data (RWD) each have their strengths and weaknesses, and can effectively complement each other. When RCTs are not feasible, RWD studies offer a valuable alternative. In this narrative review, we examine several types of RWD studies, focusing on studies utilizing administrative claims databases. These include the Diagnosis Procedure Combination databases, commercially available health checkups and healthcare claims databases (such as the JDMC and DeSC databases), and the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). Given that these claims databases cover different populations, patient settings, variables, and levels of accessibility, it is crucial for researchers to select the most appropriate data source to effectively address their research questions. Additionally, it is desirable for readers of studies using these databases to be aware of their characteristics in order to fully understand the context and limitations of the research findings.

Inter-hospital variations in the respiratory outcomes of very and extremely pre-term infants: A cohort study in Japan

BACKGROUND

Hospital-level and international variations exist in the management strategies of bronchopulmonary dysplasia (BPD). However, studies evaluating hospital-level variations in the respiratory outcomes of pre-term infants associated with differing management strategies of BPD are lacking.

OBJECTIVE

Herein, we aimed to assess inter-hospital variations in the respiratory outcomes of BPD in very pre-term and extremely pre-term infants.

METHODS

In this cohort study, the administrative claims and discharge summary data were extracted from 276 hospitals in Japan between April 2014 and March 2016. This study assessed neonates of a gestational age of 22-31 weeks old, who had been hospitalised for ≥7 days. The primary outcome was a BPD defined using any respiratory support, such as supplemental oxygen, high-flow nasal cannula, CPAP, or mechanical ventilation at 36 weeks PMA. The median odds ratio (MOR) was calculated using a multilevel logistic regression model, including baseline characteristics, comorbidities, and treatment as covariates, to evaluate the inter-hospital variation of the outcome.

RESULTS

Of the 8143 neonates from across 132 hospitals, 53.7% were male, with a mean gestational age (standard deviation) of 28.0 (2.5)-weeks-old and birthweight of 1086 (386) g. Among these patients, BPD occurred in 2737 (33.6%). The MOR was 2.49, representing the median value of odds ratios when comparing two neonates with identical covariates from hospitals with high and low propensity for the outcomes to occur.

CONCLUSIONS

Outcome variations in the BPD were observed among hospitals in Japan, even after adjusting for individual factors, including gestational age, birthweight, comorbidities, and treatments. Thus, in Japan, developing strategies is essential to decrease the BPD rates, while minimising inter-hospital heterogeneity, to improve the healthcare quality for pre-term neonates.

Updated information on the Diagnosis Procedure Combination data

The Ministry of Health, Labor, and Welfare, Japan, launched the Diagnosis Procedure Combination system in 2002. Detailed information on the Diagnosis Procedure Combination data was reported in Annals of Clinical Epidemiology in 2019. In this report, I provide updated information on the Diagnosis Procedure Combination. The data included the discharge abstracts and administrative claims data for each inpatient. Several entities (including the Ministry, academic groups, and private companies) independently collected anonymized Diagnosis Procedure Combination data. The advantages of Diagnosis Procedure Combination data include detailed process and clinical data, which enable researchers to conduct clinical epidemiology and health services research. Diagnoses are recorded using the International Classification of Diseases-10th Revision codes, and several indices based on these codes can be used. Several clinical measures are available for specific diseases including stroke, respiratory failure, heart failure, pneumonia, liver cirrhosis, pancreatitis, burns, and multiple organ failure. Scores for consciousness, activities of daily living, functional independence, and dementia are also available. Studies that use Diagnosis Procedure Combination data are interdisciplinary and include clinical medicine, epidemiology, statistics, and medical informatics.

Stroke Research Using Administrative Claims Database in Japan: A Narrative Review

AIMS

Although administrative claims databases have recently been used for clinical research in Japan, no detailed description of their utilization in stroke research is available. We reviewed stroke studies using the Diagnosis Procedure Combination (DPC), the National Database of Health Insurance Claims and Specific Health Checkups (NDB), and several commercial databases sourced from social health insurance associations, focusing on their applications and limitations.

METHODS

Original articles on stroke published by April 2024 using the DPC, NDB, and commercial databases were identified in Ovid MEDLINE. The characteristics of each database were compared in terms of comprehensiveness, traceability, baseline information, and outcome assessment in stroke research.

RESULTS

A total of 114 studies were included (83 for DPC, 6 for NDB, and 25 for commercial databases). The number of stroke studies using administrative databases in Japan is still approximately 10 per year, although there is a slowly increasing trend. The DPC database was utilized for short-term outcome studies because of its detailed baseline and outcome information, although the inability to track patients once they changed facilities limits their use in long-term studies. The NDB database is potentially useful for long-term studies because of its comprehensiveness and traceability, but difficulties in data access restrict its usage. The most commonly used commercial database utilizes baseline information on lifestyle and blood test data, although the lack of coverage for those over 75 years old may limit its generalizability.

CONCLUSIONS

Administrative claims databases are beginning to be used in stroke research in Japan but are not yet fully utilized. Researchers need to understand their applications and limitations.

Impact of new antifungal medications on onychomycosis prescriptions and costs in Japan: A nationwide claims database study

Onychomycosis, a fungal nail infection, is a common dermatological condition in Japan, with a prevalence of approximately 5%-10%. Despite the introduction of new antifungal medications and updated treatment guidelines published in 2019, data on real-world prescription trends and the associated medical costs are limited. This study aimed to investigate the prescription patterns and medical costs of topical and oral antifungal medications for onychomycosis in Japan from fiscal years 2014 to 2021 using the National Database of Health Insurance Claims and Specific Health Checkups of Japan Open Data. We analyzed the annual prescription volumes and medical costs of four antifungal medications: efinaconazole, luliconazole, fosravuconazole, and terbinafine. The prescription volume of efinaconazole, a topical medication launched in 2014, rapidly increased and dominated the market share. Fosravuconazole, an oral medication introduced in 2018, showed an increasing trend, coinciding with a decline in efinaconazole prescriptions. Terbinafine, a well-established oral medication, experienced a substantial decrease in prescription volume. The sex- and age-adjusted prescription volume per 100 000 population was higher among older adults, particularly for efinaconazole. The total medical costs for onychomycosis treatment more than doubled in fiscal year 2015 compared with that for 2014, mainly driven by efinaconazole prescriptions, and exceeded 30 billion Japanese yen in fiscal years 2019-2021. The costs slightly decreased in fiscal years 2020 and 2021, possibly due to the introduction of fosravuconazole. The predominance of topical prescriptions, especially in older adults, raises concerns regarding adherence to the Japanese guidelines that recommend oral antifungals as the first-line treatment for onychomycosis. The substantial increase in medical costs also highlights the economic burden of onychomycosis and the need for cost-effective treatment strategies. This study provides valuable insights into the real-world prescription trends and medical costs of onychomycosis treatment in Japan, suggesting an opportunity to assess potential gaps between guideline recommendations and clinical practice.

Trends in inpatient orthopedic surgery during the COVID-19 pandemic in Japan: a nationwide data study

BACKGROUND

Coronavirus disease 2019 (COVID-19) has resulted in substantial morbidity and mortality globally. The National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) covers 99.9% of health insurance claim receipts by general practitioners. The purpose of this study is to investigate the nationwide number of inpatient orthopedic surgeries in Japan during the effect of state of emergency (SoE) due to COVID-19.

METHOD

The NDB has been publicly available since 2014. We retrospectively reviewed the NDB from April 2019 to March 2022. We gathered the monthly number of all inpatient orthopedic surgeries. We also classified orthopedic surgeries into the following 11 categories by using K-codes, Japanese original surgery classification: fracture, arthroplasty, spine, arthroscopy, hardware removal, hand, infection/amputation, ligament/tendon, tumor, joint, and others. By using the average number from April to December 2019 as the reference period, we investigated the increase or decrease orthopedic surgeries during the pandemic period.

RESULTS

The NDB showed that the average number of total inpatient orthopedic surgeries during the reference period was 115,343 per month. In May 2020, monthly inpatient orthopedic surgeries decreased by 29.6% to 81,169 surgeries, accounting for 70.3% of the reference period. The second SoE in 2021 saw no change, while the third and fourth SoEs showed slight decreases compared to the reference period. Hardware removal and tumor surgeries in May 2020 decreased to 45.3% and 45.5%, respectively, while fracture surgeries had relatively small decreases.

CONCLUSION

According to NDB, approximately 1.3 million orthopedic inpatient surgeries were performed or claimed in a year in Japan. In May 2020, the first SoE period of the COVID-19 pandemic, the number of inpatient orthopedic surgeries in Japan decreased by 30%. Meanwhile, the decrease was relatively small during the SoE periods in 2021.

Updated Information on NDB

The Ministry of Health, Labour, and Welfare, Japan launched a national administrative claims database in 2009, which is called the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). Detailed information on the NDB was reported in Annals of Clinical Epidemiology in 2019. The present report provides updated information on the NDB. In 2020, the provision of data to private companies, as well as public sectors and academic entities, was legislated. As of 2024, the Ministry of Health, Labour, and Welfare is planning linkage of NDB data with several other national databases. Our previous literature review identified a total of 126 original articles using the NDB and NDB Open Data published from 2013 to 2022. Our updated review identified 94 original articles using the NDB and NDB Open Data in the recent two years. Studies using the NDB are gradually increasing, but there is still room for enhancing NDB studies on various subject areas.

The association between intraoperative anesthesia methods used during gastric cancer surgery and long-term mortality: A retrospective observational study using a Japanese claims database

PURPOSE

Various basic and clinical studies have investigated the association between the types of anesthetic agents and prognosis. However, the results have varied among studies and remain controversial. In the present study, we aimed to investigate whether the risk of all-cause mortality differs between inhaled or intravenous anesthetics in patients with gastric cancer undergoing gastrectomy.

METHODS

Using a Japanese nationwide insurance claims database, we analyzed patients who underwent gastrectomy under general anesthesia for gastric cancer between January 2005 and September 2019. Postoperative outcomes were compared between two groups: those who received inhaled anesthetics (Sevoflurane, Isoflurane, or Desflurane) and those who received intravenous anesthetics (propofol), using a multivariable Cox proportional hazards model. The primary outcome was overall survival.

RESULTS

Among 2671 eligible patients, 2105 were in the inhaled anesthetic group, and 566 were in the intravenous anesthetic group. The median (interquartile range) age was 58 (51-63) years, and 1979 (74.1%) were men. The median follow-up period was 795 days. We identified 56 (2.7%) and 16 (2.8%) deaths during the follow-up period in the inhaled and intravenous anesthetic use groups, respectively. There was no difference in postoperative overall survival between the two groups (hazard ratio, 0.97; 95% confidence interval, 0.56-1.70; P = 0.93).

CONCLUSIONS

We found no significant difference in the postoperative risks of overall survival between inhaled and intravenous anesthesia in patients with gastric cancer undergoing gastrectomy.

Validation studies of Japanese administrative health care data: A scoping review

PURPOSE

Large-scale administrative health care databases are increasingly being utilized for research. However, there has not been much literature that validated administrative data in Japan; a previous review identified six validation studies published between 2011 and 2017. We conducted a literature review of studies that assessed the validity of Japanese administrative health care data.

METHODS

We searched for studies published by March 2022 that compared individual-level administrative data with a reference standard from another data source, as well as studies that validated administrative data using other data within the same database. The eligible studies were also summarized based on characteristics which included data types, settings, reference standard used, numbers of patients, and conditions validated.

RESULTS

There were 36 eligible studies, including 29 that used external reference standard and seven that validated administrative data using other data within the same database. Chart review was the reference standard in 21 studies (range of the numbers of patients, 72-1674; 11 studies conducted in single institutions and nine studies in 2-5 institutions). Five studies used a disease registry as the reference standard. Diagnoses of cardiovascular diseases, cancer, and diabetes were frequently evaluated.

CONCLUSIONS

Validation studies are being conducted at an increasing rate in Japan, although most of them are small scale. Further large-scale comprehensive validation studies are necessary to effectively utilize the databases for research.