Geographic distribution and trends of small-area burn claims in Japan: An analysis using NDB open data from 2014 to 2021

Abstract

Introduction

Burns are a major global health issue, causing approximately 180,000 deaths annually and leading to high morbidity rates. The Japan Trauma Data Bank Report 2022 recorded 1749 burn cases, with a mortality rate of 17.6%. However, comprehensive national data regarding non-fatal burns and regional differences in Japan are lacking. This study aimed to analyze the distribution of small-area burns among patients across Japanese prefectures using the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB).

Methods

We utilized NDB Open Data from fiscal years 2014 to 2021 to investigate medical claims for small-area burns. The number of claims was normalized to the population of each prefecture using demographic data obtained from eStat, and the correlation between the number of claims and per capita income in each prefecture was assessed.

Results

The highest number of small-area burn claims was observed among children aged 0–5 years and individuals aged >65 years. Women aged 15–64 years submit approximately twice as many claims as men in the same age group. Significant geographic variations were observed, with more claims in Kochi, Saga, Kumamoto, and Kagoshima and fewer claims in Okinawa, Hokkaido, and Chiba. The number of claims decreased annually, with Saga Prefecture exhibiting the most substantial reduction. There is a significant negative correlation between the number of claims and per capita income.

Conclusion

The annual decrease in claims corresponds with previous reports of a decreased incidence of burn injuries. Regional differences suggest an influence of local factors on burn incidence. Further research is necessary to explore these regional disparities and to identify effective burn prevention strategies.

Lay summary

Burns are a major global health problem, causing many injuries and deaths each year. In Japan, severe burns are well-documented, but there is little information about small-area burns that do not require hospitalization. Understanding how often and where these small-area burns occur can help create better prevention strategies. This study aims to understand the frequency and distribution of small-area burns across different regions in Japan and among various age and gender groups. We want to identify which areas have higher or lower rates of small-area burns and observe any trends over time. We used data from Japan's National Database of Health Insurance Claims, covering 2014 to 2021. This database includes information on medical treatments paid for by health insurance. We calculated the number of small-area burns per 1000 people for each prefecture (region) in Japan and analyzed differences based on age and gender. We found small-area burns are most common among young children (aged 0–5) and older adults (over 65). Women aged 15–64 had about twice as many small-area burns as men in the same age group. There were significant regional differences: some areas, like Kochi and Saga, had higher rates of small-area burns, while others, like Okinawa and Hokkaido, had lower rates. Over the years, small-area burns decreased, with Saga showing the most notable reduction.

Our study provides valuable insights into the patterns of small-area burns in Japan, which can help in designing targeted prevention efforts. However, we did not investigate the specific reasons behind the regional differences or the decrease in burn cases over time. This underscores the need for further research to understand these factors better and potentially make more significant contributions to public health.

Keywords

Small-area burns national database of health insurance claims and specific health checkups of Japan open data Japan prefecture medical claims

Introduction

Burns are a global public health problem and are responsible for approximately 180,000 deaths annually.¹ Nonfatal burn injuries are a leading cause of morbidity.¹ The Japan Trauma Data Bank Report 2022 recorded 1749 burn cases, accounting for 2.0% of all injury cases and with a mortality rate of 17.6%.² This report, based on data from 303 hospitals in 2022, does not cover all of the 7138 general hospitals and 104,488 clinics in Japan.³ There is no comprehensive national data on burns, particularly nonfatal burns, nor are there any reports detailing the differences in burn incidence among Japanese prefectures. Investigating these differences could help to reduce the burden of burns.

Burns are categorized by depth into four types, including epidermal, superficial dermal, deep dermal, and deep burns.⁴ In Japan, medical burn claims are classified by burn area: < 100 cm², ≥ 100 and <500 cm², ≥ 500 and <3000 cm², ≥ 3000 and < 6000 cm², and ≥ 6000 cm².⁵ This study defines small area burns as covering < 100 cm². Claims for small-area burns were made when the patient was not admitted or was admitted after surgery, and did not include epidermal burns that were not treated within two months of the first treatment.

The National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) contains extensive national healthcare insurance system data.⁶ The Ministry of Health, Labour, and Welfare publishes the NDB Open Data that investigates the prevalence of surgeries and drug prescriptions.^7-11 This study aimed to reveal the distribution of small-area burns among patients in each prefecture using NDB Open Data.

Methods

We investigated medical claims for small-area burns using NDB Open Data from fiscal years (FY) 2014 to FY2021. The NDB Open Data are published on the website of Japan’s Ministry of Health, Labour, and Welfare (https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/0000177182.html). The data were published every five years and by sex. These data were also published by prefecture. The number of medical claims for small-area burns was obtained from the website. The population of each prefecture was obtained from the eStat website¹² (https://www.e-stat.go.jp/). First, we explored the correlation between the number of medical claims for small-area burns and the population in each prefecture for every FY using the Spearman’s rank correlation coefficient. Subsequently, we divided the number of medical claims for small-area burns by the population of each prefecture and calculated the number of small-area burns per 1000 people per year in each prefecture.

We investigated the age-specific distribution of medical claims for small-area burns according to sex from FY2014 to FY2021. We explored the age group with the highest number of medical claims for small-area burns by sex. We also examined the distribution of small-area burn claims in all prefectures of Japan during these periods. We created a choropleth map of small-area burn claims. Subsequently, we investigated the number of small-area burn claims per prefecture and FY area. We examined the prefecture with the highest number of medical claims for small-area burns according to sex during this period. We also investigated the prefectures that experienced a substantial decrease in small-area burn claims from FY2014 to FY2021.

Two analyses were conducted to investigate the relationship between the number of small-area burns and socio-economic factors. First, we investigated the correlation between the number of claims for small-area burns and the percentage of high school graduates who went on to higher education in FY 2021 using Spearman’s correlation coefficient. The percentage of high school graduates who proceeded to higher education in FY2021 was quoted from eStat (https://www.e-stat.go.jp/regional-statistics/ssdsview/prefectures). Second, we investigated the correlation between per-capita income and the estimated number of small-area burns in each prefecture in 2015 using Spearman’s correlation coefficient. Data detailing per capita income in each prefecture in 2015 were obtained from eStat (https://www.e-stat.go.jp/regional-statistics/ssdsview/prefectures).

Statistical analysis

Stata 18 (StataCorp, College Station, TX, USA) was used for statistical analyses. Microsoft Excel (USA) was used to create a geographic figure.

Results

The correlation between the number of small-area burn claims and the population per prefecture was significantly strong in all FYs (Figure 1).

Figure 1.

The graphs present the correlation between the number of claims for small-area burns per prefecture and the population per prefecture for the entire fiscal year. Horizontal axis: population per prefecture (thousand); vertical axis: number of claims for small-area burns. Spearman’s rank correlation coefficients are calculated as rho (ρ).

The age-specific distribution of small-area burn claims by sex is presented in Figure 2. Claims peaked among children aged 0–5 years and increased again among those aged >65 years. Women aged 15–64 years submit approximately twice as many claims as men in the same age group. The number of claims for small-area burns increased sharply among women aged >65 years compared to that of men in the same age group.

Figure 2.

Graphs indicate the distribution of claims for small-area burns across all ages by fiscal year. Upper: Men; lower: Women. Horizontal axis: age; vertical axis: number of claims for small-area burns per 1000 population.

The distribution of claims for small-area burns in each prefecture from FY2014 to FY2021 is presented in Figure 3. The maximum, median, and first and third quartiles gradually decreased. Overall, the number of claims for small-area burns decreased from FY2014 to FY2021.

Figure 3.

Distribution of the number of medical claims for small-area burns in 47 prefectures in Japan. The upper horizontal figures indicate the fiscal year.

The choropleth map revealed the geographic distribution of claims, with numerous claims in Western Japan, particularly in Kyushu (Figure 4). In Figure 4, dark red indicates a high number of medical claims for small-area burns, and light red indicates a low number. Kyushu, the third largest island in Japan, is located in the southwestern part of the country and is famous for its hot springs and active volcanoes such as Mount Aso.

Figure 4.

Choropleth map of claims for small-area burns. Dark-red indicates more claims for small-area burns, and light-red indicates fewer claims.

The prefectures with the highest number of claims were Kochi, Saga, Kumamoto, and Kagoshima (Table 1), whereas Okinawa, Hokkaido, and Chiba exhibited the fewest (Table 2). The locations of these prefectures are indicated in Figure 2.

Table 1.

Prefectures with more claims of small-area burns per 1000 population.

Year	1^st ranked	2^nd ranked	3^rd ranked	4^th ranked
2014	Saga 20.6	Kouchi 19.4	Kagoshima 17.6	Kumamoto 16.3
2015	Saga 19.6	Kouchi 18.4	Kagoshima 17.0	Kumamoto 16.7
2016	Saga 19.1	Kouchi 18.4	Kagoshima 16.1	Kumamoto 16.1
2017	Kouchi 19.8	Saga 19.2	Kumamoto 16.8	Kagoshima 16.2
2018	Saga 17.1	Kouchi 16.8	Kagoshima 14.7	Kumamoto 14.4
2019	Kouchi 15.8	Saga 15.3	Kagoshima 14.1	Kumamoto 13.3
2020	Kouchi 16.8	Saga 15.0	Kagoshima 13.7	Aomori 12.0
2021	Kouchi 15.9	Saga 14.3	Kagoshima 13.4	Kumamoto 12.4

Unit: claims of small-area burns per 1000 population.

Table 2.

Prefectures with fewer claims of small-area burns per 1000 population.

Year	1^st ranked	2^nd ranked	3^rd ranked	4^th ranked
2014	Okinawa 4.0	Hokkaidou 8.1	Chiba 8.5	Niigata 9.0
2015	Okinawa 4.0	Chiba 8.0	Hokkaidou 8.0	Akita 8.4
2016	Okinawa 4.0	Hokkaidou 7.9	Chiba 8.4	Saitama 8.6
2017	Okinawa 4.0	Hokkaidou 7.6	Chiba 8.0	Kanagawa 8.4
2018	Okinawa 3.6	Chiba 7.2	Hokkaidou 7.3	Niigata 7.5
2019	Okinawa 3.5	Chiba 6.7	Hokkaidou 7.1	Niigata 7.2
2020	Okinawa 3.5	Chiba 6.0	Hokkaidou 6.5	Saitama 6.6
2021	Okinawa 3.4	Chiba 6.2	Hokkaidou 6.3	Saitama 6.6

Unit: claims of small-area burns per 1000 population.

Saga Prefecture exhibited the most significant reduction in claims over the eight-year period (Table 3).

Table 3.

Prefectures with the highest decrease in claims of small-area burns per 1000 population.

Rank	Prefecture	Change from FY2014 to FY2021
1^st	Saga	20.6 to 14.3
2^nd	Miyazaki	16.2 to 11.1
3^rd	Tottori	14.5 to 9.8
3^rd	Hiroshima	15.4 to 10.7

Unit: claims of small-area burns per 1000 population.

The correlation between the number of claims for small-area burns and the percentage of high school graduates who went on to higher education was not statistically significant (ρ=-0.25, p = 0.09). The correlation between the number of claims for small-area burns and per capita income in each prefecture was statistically significant (ρ=-0.4, p = 0.005) (Figure 5).

Figure 5.

Graphs illustrate the correlation between the number of claims for small-area burns per prefecture and per capita income in each prefecture. Horizontal axis: per capita income in each prefecture (thousands Japanese Yen); vertical axis: number of claims for small-area burns per 1,000 population.

Discussion

This study is the first to reveal the number of small-area burn claims per 1000 people in each prefecture using the NDB Open Data and population data from FY2014 to FY2021. The number of claims decreased annually, consistent with reports of a gradual decline in patients with burns in Japan.¹³ The highest number of claims was observed among children aged <5 years and older adults aged >65 years, and this is consistent with previous results.¹⁴ Women aged 15–64 years submitted approximately twice as many claims as did men in the same age group, and this is similar to previous findings.¹⁵

Kyushu district exhibited more small-area burn claims than other regions. Prefectures such as Kochi, Saga, Kumamoto, and Kagoshima exhibited more claims than did Okinawa, Hokkaido, and Chiba. Although the reason for the consistently low number of small-area burns claims in certain prefectures remains unknown, burns caused by hot liquids such as boiling water or oil are the most common, followed by burns from contact with heating appliances.¹⁴ As reported in our study, the highest incidence of these burns occurred in children aged <5 years. Given the opportunities of young children to encounter hot objects, measures should be taken to keep them away from kitchens and heating appliances. However, electric kettles can be used to boil water anywhere (not only in the kitchen), and this may lead to a lack of preventive measures. Burns caused by boiling water in electric kettles have been reported.¹⁶ It is uncertain whether adequate attention should be paid to the dangers of electric kettles in areas with many children; however, it is essential to exercise caution. No studies have reported the geographic distribution of nonfatal burns in Japan, indicating the need for further investigation of the reasons for these regional differences.

Saga Prefecture exhibited the most substantial reduction in claims, dropping from first rank in FY2014 to second in FY2021. The reason for this reduction is unknown, and further investigation is warranted to identify potential strategies for reducing small-area burns.

This study observed a negative correlation between per-capita income and the number of medical claims for small-area burns. Previous studies have also identified an association between low income and burn incidence, and this is consistent with our findings.^17,18 However, few studies have reported an association between small-area burns and low income, as is presented here.^18,19

Limitations

This study focused on the number of medical claims for small-area burns rather than on the number of patients. Therefore, investigating the number of patients with fewer burns in each prefecture is essential. Additionally, medical claims for small-area burns may have been inaccurately reported, particularly for first-degree burns that were not classified as small-area burns in this study.

As the only data available on per capita income were from 2015, it was only possible to compare the number of medical claims for minor burns within a single year.

Despite these limitations, this study provides valuable insights into the distribution of small-area burn claims in Japan and the differences among the prefectures. There was a significant negative correlation between per-capita income and claims for small-area burns. Further research is necessary to understand these regional disparities and develop effective burn-prevention strategies.

Conclusion

To our knowledge, this is the first study to reveal the prefectural distribution of small-area burn-related claims in Japan. This annual decrease in claims corresponds to previous reports of decreased burn injuries. Regional differences suggest that local factors influence the incidence of small-area burns. Socio-economic status such as low income is related to the number of small-area burn claims. To identify effective burn prevention strategies, further research is necessary to explore regional disparities and substantial burn reductions in the Saga Prefecture.

Footnotes

ORCID iDs

Takeshi Utsunomiya

Takahiro Ueda

Ethical considerations

Authors use only open data in the research. Thus, ethical approval and informed consent were not necessary.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability statement

The data supporting this study’s findings are available at [in Japanese].

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