Background The Great East Japan Earthquake and subsequent tsunami and nuclear disaster on 11 March 2011 had a short-term influence on the increase in emergency department visits and hospital admissions due to various diseases. However, it remains unclear whether the earthquake and tsunami disaster affected the long-term health conditions of people in the affected areas.
Methods Using a national inpatient database in Japan, we investigated people's ambulatory care sensitive conditions (ACSCs), which are defined as conditions for which effective management and treatment should prevent admission to a hospital. We compared the number of admissions for ACSCs before-quake (July 2010 to February 2011) with after-quake (July 2012 to February 2013) periods in the disaster area compared with other areas using a difference-in-differences design. Linear regression models with the interaction between periods and areas were used to estimate the impact of the earthquake on admissions for ACSCs.
Results No significant difference in difference was seen in preventable ACSCs (where immunisation and other interventions can prevent illness) or chronic ACSCs (where effective care can prevent flare-ups), while acute ACSCs (where early intervention can prevent more serious progression) increased significantly (3.3 admissions per 100 000 population; 95% CI 0.4 to 6.3; p=0.028).
Conclusions Preventable and chronic ACSCs may have increased just after the earthquake and then immediately decreased. However, avoidable admissions due to acute ACSCs remained high in the long term after the earthquake and tsunami disaster.
- DISASTER RELIEF
- PRIMARY CARE
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The Great East Japan Earthquake was followed by a tsunami that hit East Japan on 11 March 2011. A total of 19 225 people died and 2614 people were still missing as of 31 March 2015.1 The earthquake and tsunami severely destroyed the Pacific coastline of the Tohoku region, and the subsequent accident at the Fukushima Daiichi nuclear power plant forced nearly 180 000 people to evacuate.2–4
The earthquake and the following tsunami completely destroyed 10 of the 380 hospitals and partially destroyed 290 of the 380 hospitals in the Tohoku region, and many hospitals lost their capacity to function. In addition, the government ordered mandatory evacuation of the area surrounding the Fukushima Daiichi nuclear power plant. Hospitals and clinics within this area were unavoidably closed. As a result, 19 of the 33 hospitals located in the disaster zone had restricted inpatient care capacity 3 months after the earthquake.5 Such a situation may have impaired access to primary and secondary care for people in the most affected areas.
Previous studies have reported that earthquakes are associated with long-term physical6 and mental7 ,8 disorders. Other studies have shown the short-term influence of the Great East Japan Earthquake and tsunami disaster on increases in emergency department visits and hospital admissions due to cardiovascular disease,9 ,10 cerebrovascular disease,9 ,11 respiratory disease,9 ,12–14 infectious disease,15 gastrointestinal bleeding16 and others.9 ,17 However, it remains unknown whether the earthquake and tsunami disaster affected long-term health conditions of people in the affected areas.
The objective of the present study was to investigate the influence of the Great East Japan Earthquake and subsequent tsunami and nuclear disasters on people's long-term health conditions in terms of their ambulatory care sensitive conditions (ACSCs),18–20 using a national inpatient database in Japan. On the basis of the results, we aim to discuss the resilience of the Japanese universal health coverage system against devastating natural disasters.
Data source and population
In this retrospective two-stage cross-sectional study, patient data for this study were extracted from the Japanese Diagnosis Procedure Combination inpatient database.21 ,22 The database includes data from ∼7 million inpatients at more than 1000 hospitals, which represents ∼50% of all discharges from acute care hospitals in Japan. Hospital data were extracted from the Survey of Medical Institutions data in Japan, which includes each hospital's address and number of acute care beds.
We extracted data on patients aged 20 years and above on all hospital admissions due to ACSCs from July 2010 to March 2013. Data included age, sex and zip code of the patient's residence; diagnoses coded with International Classification of Diseases, 10th Revision (ICD-10) and Charlson Comorbidity Index23 codes; and length of stay. Hospital data included type of hospital (academic or non-academic) and the number of beds in each hospital. We only included people aged 20 years or older because the reasons for admission of younger aged people may be different from those for adults. The Charlson Comorbidity Index is widely used to measure 17 comorbidities based on administrative data.23 Each comorbidity category has a weight, and the sum of all the weights results in a single index ranging from 0 to 24.23 We defined the period between July 2010 and February 2011 as ‘before the quake’ because data from July 2010 are available in the Diagnosis Procedure Combination (DPC) database. We regarded the period between July 2012 and February 2013 as ‘after the quake’ to avoid the influence of seasonal variation in certain conditions.
Ambulatory care sensitive conditions
ACSCs are defined as conditions for which appropriate intervention in primary care could prevent admission to a hospital.18 ,19 ACSCs have been used as indicators of the accessibility and quality of primary care.20 High frequencies in admissions for ACSCs indicate poor coordination between primary and secondary care. An avoidable admission for an ACSC indicates poor overall quality of care, even if the ACSC episode itself is well managed.19
The outcomes of this study compared pre-quake and post-quake hospital admissions for the following three types of ACSCs: (1) preventable ACSCs (where immunisation and other interventions can prevent illness, eg, influenza and pneumonia); (2) chronic ACSCs (where effective care can prevent flare-ups, eg, asthma, congestive heart failure, diabetes complications, chronic obstructive pulmonary disease, angina, iron deficiency anaemia, hypertension and nutritional deficiency); and (3) acute ACSCs (where early intervention can prevent more serious progression, eg, dehydration and gastroenteritis; pyelonephritis; perforated/bleeding ulcer; cellulitis; pelvic inflammatory diseases; ear, nose and throat infections; dental conditions; convulsions and epilepsy; and gangrene); and (4) overall ACSCs (composite of the preceding 3 ACSCs). Table 1 shows the ICD-10 codes used to identify the 19 ACSCs commonly used in the National Health Service in the UK.18
Continuous variables are presented as the mean and SD and/or the median and IQR. Categorical variables are presented as the number and percentage. Admissions for overall and individual types of ACSCs are presented as the mean number of admissions per 100 000 people and 95% CI. To estimate the number of admissions for ACSCs, we developed an analytic data set by stratifying all patients according to age category, sex, prefecture, hospital bed category (categorised by the number of acute care beds in 6 categories) and admission month. We created 91 678 observations through this stratification (excluding units without any patients). We obtained the population corresponding to each stratified unit from the Population Census reported by the Statistics Bureau of Japan. All patients were stratified in 5-year intervals because of the minimum granularity of the available census data.
The associations between an unexpected event and subsequent outcomes are often evaluated using a before-and-after design, that is, the outcomes after the event are compared with outcomes before the event. This design is invalid if there are underlying time-dependent trends in outcomes that are unrelated to the event. If outcomes were already getting worse before the event, then use of a before-and-after design would lead to the erroneous conclusion that the event was associated with worse outcomes. The difference-in-differences design addresses this problem by using a comparison group that is experiencing the same trends, but was not exposed to the event. Two differences should be estimated: the difference between after and before the event in the group exposed to the event (D1) and the difference between after and before the date of the event in the unexposed group (D2). The change in outcomes related to the event beyond the background trends can then be estimated using the difference-in-differences analysis as D1–D2.24
Previous studies assessed the association of the Great East Japan Earthquake with increases in disease incidence using a before-and-after design. In this study, we used a difference-in-differences design to address potential time-dependent trends in ACSCs unrelated to the earthquake.
The number of admissions for ACSCs per 100 000 people was estimated with the following equation:
where Yi is the estimated proportion of admissions for ACSCs for each unit, Ni is the observed number of admissions for ACSCs for each unit, Hall is the number of all hospitals in each unit, and HDPC is the number of hospitals which participated in the database in each unit. From the aforementioned equation, the outcome of interest becomes the proportion of admissions for ACSCs providing continuous data. Therefore, we selected linear regression models. Independent variables were periods (before and after the Earthquake), areas (the affected areas including Fukushima, Miyagi and Iwate prefectures, and other areas), and the interaction of these two variables (to estimate the difference in differences of the number of admissions per 100 000 people). All analyses were performed using SPSS V.22.0.
A total of 998 403 patients were admitted for ACSCs during the study period. After excluding those who were admitted to hospitals with missing information, 952 127 patients were included in the analysis. Of those, 36 564 (3.8%) were admitted in the disaster-affected areas, and 915 563 (96.2%) were admitted in other areas. Table 2 shows the characteristics of patients who were admitted for ACSCs. Although the differences were statistically significant, differences in age and sex were clinically insignificant between disaster-affected and other areas before and after the earthquake and tsunami disaster.
Table 3 shows the numbers of admissions for ACSCs per 100 000 people living in disaster-affected and other areas before and after the earthquake. Overall, ACSCs increased after the quake both in the disaster area (5.8 admissions per 100 000 population) and other areas (2.3 admissions per 100 000 population), and the increments were not significantly different between the disaster-affected and other areas (3.8; 95% CI −5.0 to 12.6). Similar findings were observed for admissions due to preventable and chronic ACSCs. Admissions for acute ACSCs significantly increased in the disaster area compared with the other areas (3.3, 95% CI 0.4 to 6.3).
Table 4 shows the numbers of admissions for residents of the disaster area stratified by location of hospital. Residents of the disaster area who were admitted to hospitals outside the disaster area before and after the earthquake made up 1.9% and 2.5% of the total residents of the disaster area, respectively.
In this retrospective two-stage cross-sectional study using a national inpatient database, admissions for acute ACSCs were significantly increased at 16–24 months after the Great East Japan Earthquake and tsunami disaster. The earthquake was not significantly associated with changes in admissions for overall, preventable or chronic ACSCs.
Our results showed that admissions for preventable and chronic ACSCs did not increase 16–24 months after the earthquake and tsunami disaster. These conditions may have increased just after the disaster, and immediately decreased thereafter. In fact, several studies reported that the increase in such conditions was temporary and that they started to decrease several weeks after the earthquake and tsunami disaster.9 ,10 ,12 ,14–16
Previous studies have used a before-and-after design.9–12 ,14–16 However, this design may not be appropriate to account for underlying time-dependent trends in admissions for ACSCs. Also, most of the previous studies were based on a single health facility. This study is advantageous in that it used a difference-in-differences design, using nationwide inpatient data.
Our study deserves comparison with studies on the health impacts of other natural disasters. Limited studies such as those after Hurricane Katrina have investigated the impact of natural disasters on long-term health consequences in North America. Several studies suggest that Hurricane Katrina had negative impacts on the management of chronic conditions,25 ,26 while the incidence of several conditions including cardiovascular disease and cerebrovascular disease increased after the storm.27–30 The populations devastated most by Hurricane Katrina were the poor and the uninsured.31 Nearly 50% of evacuees living in shelters were uninsured.32 The lack of health insurance may have affected the long-term health consequence of people living in the hurricane-hit areas.
In contrast to Hurricane Katrina, the Great East Japan Earthquake was not associated with changes in admissions for chronic ACSCs. One possible explanation for this discrepancy may be differing proportions of the insured and the uninsured between Japan and the USA. Unlike in the USA, universal health coverage has been achieved in Japan. Despite the increased incidence of a variety of diseases just after the earthquake and tsunami disaster,9–17 residents of the Tohoku region may have been able to receive appropriate management for chronic conditions once the healthcare system recovered.
Our results show that admissions for acute ACSCs increased after the earthquake and tsunami disaster. The Great East Japan Earthquake was unique in that most victims were not devastated by the earthquake itself, but by a tsunami, which was rarely seen in previous disasters.13 Emergency medical teams gathered in the disaster area could not provide sufficient medical care because many victims had died before the rescue teams arrived. Therefore, all that the healthcare professionals could do was to prevent exacerbation of chronic comorbidities in the disaster area.13 Our results indicate that the primary healthcare system providing early intervention for acute diseases may remain impaired in the affected areas.
Our results have important implications for reducing avoidable admissions in postdisaster settings; that is, avoidable admissions due to acute ACSCs may remain in the long term after a disaster. A previous study investigating the long-term impact of the Sumatra Earthquake in Indonesia in 200433 found that older age and worse physical health status were associated with increased risk of hospital admission. Focusing on residents who are older and have worse health status may be one possible strategy to decrease avoidable admissions for acute ACSCs. Further research is warranted to investigate effective strategies to improve access to early intervention to prevent disease exacerbation and reduce avoidable hospital admissions.
Some residents of the disaster-affected areas may have been admitted to hospitals in other areas, possibly due to evacuation or relocation. However, our results showed that the proportion of hospital admissions in other areas for residents of the affected areas was small.
Our study has several limitations. First, we assessed ACSCs as long-term health conditions; however, we could not directly measure outpatient care due to lack of outpatient data. Also, we could not assess the baseline health and socioeconomic status (eg, income, type of insurance) of the residents. Second, the validity of ACSCs in Japanese clinical settings remains to be further examined. Third, the difference in admission policy between hospitals might have biased the results. Fourth, we were unable to track whether patients were admitted to another hospital after discharge, and thus our analysis did not account for patients with repeated admissions. Finally, for evacuees who had lived in the exclusion zone, out-of-pocket payments for healthcare charges were exempted during the time our study was conducted. Such a policy might have affected their consumption of healthcare services.
In conclusion, the Great East Japan Earthquake was not associated with increased hospital admissions for preventable or chronic ACSCs, but was associated with a significant increase in acute ACSCs where early intervention can prevent disease progression and subsequent hospital admission.
What is already known on this subject
The Great Earthquake and the following tsunami hit Japan on 11 March 2011. The majority of hospitals in the quake-hit area had lost their function and had restricted in-patient care capacity. Studies have shown the short-term influence on the increase in emergency department visits and hospital admissions due to various diseases after the earthquake.
What this study adds
Preventable ambulatory care sensitive conditions (where immunisation and other interventions can prevent illness) and chronic ambulatory care sensitive conditions (where effective care can prevent flare-ups) did not increase significantly, while acute ambulatory care sensitive conditions (where early intervention can prevent more serious progression) increased significantly 16–24 months after the disaster. Early intervention focusing on these conditions may be necessary for residents in disaster areas to reduce avoidable admissions.
Contributors YS, HM, HY and KF contributed to the study design, analysis and interpretation of results and to the writing of the manuscript. HY and KF contributed to the data preparation.
Funding Research on Policy Planning and Evaluation from the Ministry of Health, Labour and Welfare, Japan (H26-Global Health-General-001, H27-Policy-Designated-009 and H27-Policy-Strategy-011).
Competing interests None declared.
Ethics approval The Institutional Review Board of the University of Tokyo approved this study. Informed consent was waived due to the anonymous nature of the data.
Data sharing statement The database is available only for members of the research team.