Low-flow time and outcomes in hypothermic cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation: a secondary analysis of a multi-center retrospective cohort study.

BACKGROUND: In out-of-hospital cardiac arrest (OHCA) patients with extracorporeal cardiopulmonary resuscitation (ECPR), the association between low-flow time and outcomes in accidental hypothermia (AH) patients compared to those of patients without AH has not been fully investigated. METHODS: This was a secondary analysis of the retrospective multicenter registry in Japan. We enrolled patients aged ≥ 18 years who had been admitted to the emergency department for OHCA and had undergone ECPR between January, 2013 and December, 2018. AH was defined as an arrival body temperature below 32 °C. The primary outcome was survival to discharge. Cubic spline analyses were performed to assess the non-linear associations between low-flow time and outcomes stratified by the presence of AH. We also analyzed the interaction between low-flow time and the presence of AH. RESULTS: Of 1252 eligible patients, 105 (8.4%) and 1147 (91.6%) were in the AH and non-AH groups, respectively. Median low-flow time was 60 (47-79) min in the AH group and 51 (42-62) min in the non-AH group. The survival discharge rates in the AH and non-AH groups were 44.8% and 25.4%, respectively. The cubic spline analyses showed that survival discharge rate remained constant regardless of low-flow time in the AH group. Conversely, a decreasing trend was identified in the survival discharge rate with longer low-flow time in the non-AH group. The interaction analysis revealed a significant interaction between low-flow time and AH in survival discharge rate (p for interaction = 0.048). CONCLUSIONS: OHCA patients with arrival body temperature < 32 °C who had received ECPR had relatively good survival outcomes regardless of low-flow time, in contrast to those of patients without AH.

Exploring the efficacy of routine antimicrobial therapy in severe fever with thrombocytopenia syndrome: Overlap weighting analysis using a nationwide inpatient database.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an infectious disease that presents a formidable challenge due to the absence of established therapeutic strategies that are explicitly tailored to its management. This study aimed to assess the impact of routine antimicrobial therapy on patients diagnosed with SFTS in Japan. We conducted a comprehensive retrospective cohort analysis using extensive data from a national inpatient database. METHODS: This study scrutinized data from adult patients with SFTS and categorized them based on whether they received antimicrobial treatment within the initial 2 days of hospital admission. A meticulous evaluation was carried out on a range of outcomes, such as in-hospital mortality rates, overall costs associated with hospitalization, and length of hospital stay. Overlap weighting was applied along with multivariate regression models to enhance the reliability of the findings through confounder adjustment. The outcomes showed no significant improvement in the prognosis of patients with SFTS who received routine antimicrobial therapy. The use of antimicrobials did not yield statistically significant improvements in in-hospital mortality rates or other secondary outcomes, suggesting that such therapeutic interventions may not be necessary during the early stages of hospital admission. CONCLUSION: In our study, administration of antimicrobials within 2 days of admission for SFTS did not affect prognosis. The standard use of antimicrobial treatments may be an issue that should be reconsidered.

Treatment and Outcomes of 844 Cases of Pneumothorax in Heritable Connective Tissue Disorders.

BACKGROUND: Characteristics, practice patterns, and clinical outcomes of secondary spontaneous pneumothorax (SSP) with heritable connective tissue disorders (Marfan, Ehlers-Danlos, and Birt-Hogg-Dubé syndromes) are unclear. METHODS: A nationwide Japanese inpatient database that included data of 524 patients with SSP (884 hospitalizations) and 137,821 with primary spontaneous pneumothorax between July 2010 and March 2020 was used in this study. Hospitalization for SSP (n = 884) was categorized into surgical (n = 459) and nonsurgical (n = 425) groups, and the patient characteristics, treatment, and outcomes were compared between the groups. Multivariable analyses were performed to evaluate risk factors for pneumothorax recurrence. We also compared the characteristics of patients with different underlying heritable connective tissue disorders. RESULTS: Compared with the nonsurgical group, the surgical group had less frequent readmission for pneumothorax (26% vs 44%; hazard ratio, 0.47; 95% CI, 0.38-0.58). Young patients (2.46; 1.83-3.32) or those with Birt-Hogg-Dubé syndrome (2.53; 1.77-3.63) had a high risk of recurrence. Pneumothorax occurred frequently in teenagers with Marfan syndrome, in those aged 20 to 39 years with Ehlers-Danlos syndrome, and in those aged ≥40 years with Birt-Hogg-Dubé syndrome. CONCLUSIONS: Detailed information on the characteristics and clinical course of SSP in heritable connective tissue disorders will aid in the clinical decision-making process.

Hospital and regional variations in intensive care unit admission for patients with invasive mechanical ventilation.

BACKGROUND: Patients who receive invasive mechanical ventilation (IMV) in the intensive care unit (ICU) have exhibited lower in-hospital mortality rates than those who are treated outside. However, the patient-, hospital-, and regional factors influencing the ICU admission of patients with IMV have not been quantitatively examined. METHODS: This retrospective cohort study used data from the nationwide Japanese inpatient administrative database and medical facility statistics. We included patients aged ≥ 15 years who underwent IMV between April 2018 and March 2019. The primary outcome was ICU admission on the day of IMV initiation. Multilevel logistic regression analyses incorporating patient-, hospital-, or regional-level variables were used to assess cluster effects by calculating the intraclass correlation coefficient (ICC), median odds ratio (MOR), and proportional change in variance (PCV). RESULTS: Among 83,346 eligible patients from 546 hospitals across 140 areas, 40.4% were treated in ICUs on their IMV start day. ICU admission rates varied widely between hospitals (median 0.7%, interquartile range 0-44.5%) and regions (median 28.7%, interquartile range 0.9-46.2%). Multilevel analyses revealed significant effects of hospital cluster (ICC 82.2% and MOR 41.4) and regional cluster (ICC 67.3% and MOR 12.0). Including patient-level variables did not change these ICCs and MORs, with a PCV of 2.3% and - 1.0%, respectively. Further adjustment for hospital- and regional-level variables decreased the ICC and MOR, with a PCV of 95.2% and 85.6%, respectively. Among the hospital- and regional-level variables, hospitals with ICU beds and regions with ICU beds had a statistically significant and strong association with ICU admission. CONCLUSIONS: Our results revealed that primarily hospital and regional factors, rather than patient-related ones, opposed ICU admissions for patients with IMV. This has important implications for healthcare policymakers planning interventions for optimal ICU resource allocation.

Current Clinical Practice of Laboratory Testing of the Hemostasis and Coagulation System in Patients with Sepsis: A Nationwide Observational Study in Japan.

Introduction: The clinical benefit of hemostasis molecular indicators such as thrombin-antithrombin complex (TAT), soluble fibrin (SF), and prothrombin fragment 1 + 2 (F1+2) for the diagnosis of disseminated intravascular coagulation (DIC) is reported. Recently, novel DIC diagnostic criteria that adopt them were proposed in Japan. Despite the theoretical understanding of their function, the practical use of these markers remains unclear. The present study aimed to provide a descriptive overview of current clinical practice regarding the measurement of hemostasis markers in sepsis management in Japan. Methods: This retrospective observational analysis used the Japanese Diagnosis Procedure Combination inpatient database containing data from more than 1500 acute-care hospitals in Japan. We identified adult patients hospitalized for sepsis between April 2018 and March 2021. Descriptive statistics for measuring several hemostasis laboratory markers were summarized using patient disease characteristics, hospital characteristic, and geographical location. Results: This study included 153,474 adult sepsis patients. Crude in-hospital mortality was 30.0%. Frequency of measurement of fibrinogen, fibrin degradation products (FDP), and D-dimer in sepsis patients on admission was 43.2%, 36.1%, and 46.4%, respectively. Novel and specific hemostasis molecular markers such as TAT, SF, and F1+2 were seldom measured (1.9%, 1.7%, and 0.02%, respectively). Hemostasis molecular markers were more frequently measured with progression of thrombocytopenia. Measurement of these clinically favorite hemostasis markers was influenced not only by disease characteristics but also hospital characteristic or geographical location. Conclusions: Hemostasis molecular markers such as TAT, SF, and F1+2 were rarely measured in clinical settings. Although adopted by several DIC scoring systems, neither fibrinogen, FDP, nor D-dimer was routinely measured.

Impact of government-issued financial incentive to medical facilities on management of secondary dysmenorrhea.

AIM: In April 2020, the Japanese government introduced a Specific Medical Fee for managing secondary dysmenorrhea (SD). This initiative provided financial incentives to medical facilities that provide appropriate management of SD with hormonal therapies. We aimed to assess how this policy affects the management processes and outcomes of patients with SD. METHODS: Using a large Japanese administrative claims database, we identified outpatient visits of patients diagnosed with SD from April 2018 to March 2022. We used an interrupted time-series analysis and defined before April 2020 as the pre-introduction period and after April 2020 as the post-introduction period. Outcomes were the monthly proportions of outpatient visits due to SD and hormonal therapy among women in the database and the proportions of outpatient visits for hormonal therapy and continuous outpatient visits among patients with SD. RESULTS: We identified 815 477 outpatient visits of patients diagnosed with SD during the pre-introduction period and 920 183 outpatient visits during the post-introduction period. There were significant upward slope changes after the introduction of financial incentives in the outpatient visits due to SD (+0.29% yearly; 95% confidence interval, +0.20% to +0.38%) and hormonal therapies (+0.038% yearly; 95% confidence interval, +0.030% to +0.045%) among the women in the database. Similarly, a significant level change was observed after the introduction of continuous outpatient visits among patients with SD (+2.68% monthly; 95% confidence interval, +0.87% to +4.49%). CONCLUSIONS: Government-issued financial incentives were associated with an increase in the number of patients diagnosed with SD, hormonal therapies, and continuous outpatient visits.

Impact of COVID-19 pandemic on the number of otolaryngologic surgeries in Japan.

OBJECTIVE: Previous studies show that the COVID-19 pandemic affected the number of surgeries performed. However, data on the association between the COVID-19 pandemic and otolaryngologic surgeries according to subspecialties are lacking. This study was performed to evaluate the impact of the COVID-19 pandemic on various types of otolaryngologic surgeries. METHODS: We retrospectively identified patients who underwent otolaryngologic surgeries from April 2018 to February 2021 using a Japanese national inpatient database. We performed interrupted time-series analyses before and after April 2020 to evaluate the number of otolaryngologic surgeries performed. The Japanese government declared its first state of emergency during the COVID-19 pandemic in April 2020. RESULTS: We obtained data on 348,351 otolaryngologic surgeries. Interrupted time-series analysis showed a significant decrease in the number of overall otolaryngologic surgeries in April 2020 (-3619 surgeries per month; 95% confidence interval, -5555 to -1683; p < 0.001). Removal of foreign bodies and head and neck cancer surgery were not affected by the COVID-19 pandemic. In the post-COVID-19 period, the number of otolaryngologic surgeries, except for ear and upper airway surgeries, increased significantly. The number of tracheostomies and peritonsillar abscess incisions did not significantly decrease during the COVID-19 pandemic. CONCLUSION: The COVID-19 pandemic was associated with a decrease in the overall number of otolaryngologic surgeries, but the trend differed among subspecialties.

Analysis of Differences in Characteristics of High-Risk Endemic Areas for Contracting Japanese Spotted Fever, Tsutsugamushi Disease, and Severe Fever With Thrombocytopenia Syndrome.

Background: Tick-borne infections, including tsutsugamushi disease, Japanese spotted fever, and severe fever with thrombocytopenia syndrome (SFTS), are prevalent in East Asia with varying geographic distribution and seasonality. This study aimed to investigate the differences in the characteristics among endemic areas for contracting each infection. Methods: We conducted an ecologic study in Japan, using data from a nationwide inpatient database and publicly available geospatial data. We identified 4493 patients who were hospitalized for tick-borne infections between July 2010 and March 2021. Mixed-effects modified Poisson regression analysis was used to identify factors associated with a higher risk of contracting each tick-borne disease (Tsutsugamushi, Japanese spotted fever, and SFTS). Results: Mixed-effects modified Poisson regression analysis revealed that environmental factors, such as temperature, sunlight duration, elevation, precipitation, and vegetation, were associated with the risk of contracting these diseases. Tsutsugamushi disease was positively associated with higher temperatures, farms, and forests, whereas Japanese spotted fever and SFTS were positively associated with higher solar radiation and forests. Conclusions: Our findings from this ecologic study indicate that different environmental factors play a significant role in the risk of transmission of tick-borne infections. Understanding the differences can aid in identifying high-risk areas and developing public health strategies for infection prevention. Further research is needed to address causal relationships.

Analysis of the effectiveness of combination antimicrobial therapy for Legionnaires' disease: A nationwide inpatient database study.

OBJECTIVES: The effectiveness of monotherapy and combination therapy with quinolones and macrolides for treating Legionnaires' disease remains uncertain; this study aimed to assess the comparative effectiveness of three treatment approaches. METHODS: Using a nationwide inpatient database, we analyzed 3560 eligible patients hospitalized for Legionnaires' disease between April 1, 2014, and March 31, 2021; patients were divided into combination therapy, quinolone monotherapy, and macrolide monotherapy groups according to the antibiotics administered within 2 days of admission. We compared in-hospital mortality, total hospitalization costs, and length of stay across these groups using multiple propensity score analysis with inverse probability of treatment weighting. RESULTS: Of the 3560 patients, there were 564 (15.8%), 2221 (62.4%), and 775 (21.8%) patients in the combination therapy, quinolone monotherapy, and macrolide monotherapy groups, respectively. No significant differences were observed in in-hospital mortality between combination therapy and quinolone monotherapy groups, and between combination therapy and macrolide monotherapy groups. There were no significant differences in total hospitalization costs or length of stay among the three groups. CONCLUSION: The study suggests that there may not be a significant advantage in using a combination of quinolones and macrolides over monotherapy for the treatment of Legionnaires' disease. Given the potential for increased side effects, careful consideration is advised when choosing this combination therapy.

Association between regional critical care capacity and the incidence of invasive mechanical ventilation for coronavirus disease 2019: a population-based cohort study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has exposed critical care supply shortages worldwide. This study aimed to investigate the association between regional critical care capacity and the incidence of invasive mechanical ventilation following novel COVID-19 during the pandemic in Japan, a country with a limited intensive care unit (ICU) bed capacity of a median of 5.1 ICU beds per 100,000 individuals. METHODS: This population-based cohort study used data from the CRoss Icu Searchable Information System database and publicly available databases provided by the Japanese government and Japanese Society of Intensive Care Medicine. We identified patients recently diagnosed with COVID-19, those who received invasive mechanical ventilation, and those who received extracorporeal membrane oxygenation (ECMO) between February 2020 and March 2023. We analyzed the association between regional critical care capacity (ICU beds, high-dependency care unit (HDU) beds, resource-rich ICU beds, and intensivists) and the incidence of invasive mechanical ventilation, ECMO, and risk-adjusted mortality across 47 Japanese prefectures. RESULTS: Among the approximately 127 million individuals residing in Japan, 33,189,809 were recently diagnosed with COVID-19, with 12,203 and 1,426 COVID-19 patients on invasive mechanical ventilation and ECMO, respectively, during the study period. Prefecture-level linear regression analysis revealed that the addition of ICU beds, resource-rich ICU beds, and intensivists per 100,000 individuals increased the incidence of IMV by 5.37 (95% confidence interval, 1.99-8.76), 7.27 (1.61-12.9), and 13.12 (3.48-22.76), respectively. However, the number of HDU beds per 100,000 individuals was not statistically significantly associated with the incidence of invasive mechanical ventilation. None of the four indicators of regional critical care capacity was statistically significantly associated with the incidence of ECMO and risk-adjusted mortality. CONCLUSIONS: The results of prefecture-level analyses demonstrate that increased numbers of ICU beds, resource-rich ICU beds, and intensivists are associated with the incidence of invasive mechanical ventilation among patients recently diagnosed with COVID-19 during the pandemic. These findings have important implications for healthcare policymakers, aiding in efficiently allocating critical care resources during crises, particularly in regions with limited ICU bed capacities. Registry and the registration no. of the study/trial The approval date of the registry was August 20, 2020, and the registration no. of the study was lUMIN000041450.

Impact of the health policy for interdisciplinary collaborative rehabilitation practices in intensive care units: A difference-in-differences analysis in Japan.

BACKGROUND: Early rehabilitation in intensive care units (ICUs) may be beneficial but is not routinely performed for adults with critical illness. In April 2018, the Japanese government introduced a health policy to provide financial incentives to hospitals that met the requirements of interdisciplinary collaboration and had teams specialized in ICU rehabilitation practices. OBJECTIVES: The present study aimed to investigate whether the health policy is associated with improved clinical practices of ICU rehabilitation. METHODS: Using a nationwide administrative inpatient database and hospital statistics data from Japan, we identified hospitals that admitted adult patients to the ICU within two days of hospital admission from April 2016 to March 2019. Using hospital-level propensity score matching, we created matched cohorts of 101,203 patients from 108 intervention hospitals that introduced the health policy, and 106,703 patients from 108 control hospitals that did not. We then conducted patient-level difference-in-differences analyses to examine changes in the percentage of patients from the intervention and control hospitals, who underwent early ICU rehabilitation within two days of ICU admission before and after the implementation of the health policy. RESULTS: In the intervention group, patients undergoing early ICU rehabilitation increased from 10% and 36% after the policy implementation. In the control group, it increased from 11% to 13%. The difference-in-difference in the percentage of patients who underwent early ICU rehabilitation between the two groups was 24% (95% confidence interval, 19%-29%). CONCLUSIONS: Early ICU rehabilitation can be facilitated by financial incentives for hospitals that engage in interdisciplinary collaboration with specialist teams. IMPLICATIONS FOR CLINICAL PRACTICE: Our Findings are relevant for hospital administrators, professional organizations, and policymakers in other nations considering strategies to support the additional deployment burdens of early ICU rehabilitation. Future studies need to explore the long-term effects and sustainability of the observed improvements in ICU rehabilitation practices.

Intracranial Pressure Monitoring in Children With Severe Traumatic Brain Injury: A Propensity Score Matching Analysis Using a Nationwide Inpatient Database in Japan.

BACKGROUND AND OBJECTIVES: Clinical benefits of intracranial pressure (ICP) monitoring in the management of children with severe traumatic brain injury (TBI) are not universally agreed upon. We investigated the association between ICP monitoring and outcomes in children with severe TBI using a nationwide inpatient database. METHODS: This observational study used the Japanese Diagnostic Procedure Combination inpatient database from July 1, 2010, to March 31, 2020. We included patients younger than 18 years, admitted to the intensive care unit or high-dependency unit with severe TBI. Patients who died or were discharged on the day of admission were excluded. One-to-four propensity score matching was performed to compare patients who underwent ICP monitoring on the day of admission with those who did not. The primary outcome was in-hospital mortality. Mixed-effects linear regression analysis compared outcomes and estimated the interaction between ICP monitoring and subgroups in matched cohorts. RESULTS: Of the 2116 eligible children, 252 received ICP monitoring on the day of admission. One-to-4 propensity score matching selected 210 patients who had ICP monitoring on admission day and 840 patients who did not. In-hospital mortality was significantly lower in patients who underwent ICP monitoring than those who did not (12.7% vs 17.9%; within-hospital difference, -4.2%; 95% CI, -8.1% to -0.4%). There was no significant difference in the proportion of unfavorable outcomes (Barthel index <60 or death) at discharge, proportion of enteral nutrition at discharge, length of hospital stay, and total hospitalization cost. Subgroup analyses demonstrated a quantitative interaction between ICP monitoring and the Japan Coma Scale ( P < .001). CONCLUSION: ICP monitoring was associated with lower in-hospital mortality in children with severe TBI. Our results demonstrated the clinical benefits of ICP monitoring in managing pediatric TBI. The advantages of ICP monitoring may be amplified in children who exhibit the most severe disturbances of consciousness.

Trends in inpatient antimicrobial consumption using days of therapy and days of antibiotic spectrum coverage: A nationwide claims database study in Japan.

INTRODUCTION: Days of antibiotic spectrum coverage (DASC), a novel metric for both antimicrobial volume and spectrum, was proposed to measure inpatient antimicrobial consumption in 2022. The DASC may better reflect efforts toward antimicrobial stewardship; however, no previous study has described the distribution of trends in DASC in hospitals or the association between the trend in DASC and days of therapy (DOT). This study assessed trends in antimicrobial consumption for inpatients at acute care hospitals in Japan using the DOT and DASC. METHODS: This retrospective observational study used the nationwide administrative inpatient claims database of Japanese acute care hospitals between 2014 and 2018. The prescriptions of all antibiotics were identified to calculate DOT/1000 patient-days, DASC/1000 patient-days, and DASC/DOT. We described the five-year trend in these metrics and examined the association between the trends in DOT and DASC. RESULTS: In total, 26,301,685 admissions from 634 hospitals were included. The DOT/1000 patient-days and DASC/1000 patient-days increased significantly by 6.1% and 5.6%, respectively. The DASC/DOT ratio did not change significantly (P = 0.35). Moreover, there was little correlation between DOT/1000 patient-days and DASC/DOT (R2 = 0.01). There was also little correlation between the five-year changes in DOT/1000 patient-days and those in DASC/DOT (R2 = 0.02). CONCLUSIONS: It may be difficult to assess trends in the antibiotic spectrum using DASC alone. However, the combination of DOT as a quantity indicator and DASC/DOT as a spectrum indicator may allow for a more appropriate evaluation of stewardship efforts.

Low-flow time and outcomes in out-of-hospital cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation.

INTRODUCTION: In out-of-hospital cardiac arrest (OHCA) patients with extracorporeal cardiopulmonary resuscitation (ECPR), the association between low-flow time, the duration between the initiation of conventional cardiopulmonary resuscitation and the establishment of ECPR, and outcomes has not been clearly determined. METHODS: This was a secondary analysis of the retrospective multicenter registry in Japan. This study registered patients ≥18 years old who were admitted to the emergency department for OHCA and underwent ECPR between January, 2013 and December, 2018. Low-flow time was defined as the time from initiation of conventional cardiopulmonary resuscitation to the establishment of ECPR, and patients were categorized into two groups according to the visualized association of the restricted cubic spline curve. The primary outcome was survival discharge. Cubic spline analyses and multivariable logistic regression analyses were performed to assess the nonlinear associations between low-flow time and outcomes. RESULTS: A total of 1,524 patients were included. The median age was 60 years, and the median low-flow time was 52 (42-53) mins. The overall survival at hospital discharge and favorable neurological outcomes were 27.8% and 14.2%, respectively. The cubic spline analysis showed a decreased trend of survival discharge rates and favorable neurological outcomes with shorter low-flow time between 20 and 60 mins, with little change between the following 60 and 80 mins. The multivariable logistic regression analyses showed that patients with long low-flow time (>40 mins) compared to those with short low-flow time (0-40 mins) had significantly worse survival (adjusted odds ratio 0.42; 95% confidence intervals, 0.31-0.57) and neurological outcomes (0.65; 0.45-0.95, respectively). CONCLUSIONS: The survival discharge and neurological outcomes of patients with low-flow time shorter than 40 min are better than those of patients with longer low-flow time.

Association Between Intraoperative Landiolol Use and In-Hospital Mortality After Coronary Artery Bypass Grafting: A Nationwide Observational Study in Japan.

BACKGROUND: Ischemic heart disease is a leading cause of death worldwide, and coronary artery bypass grafting (CABG) is a major treatment. Landiolol is an ultra-short-acting beta-antagonist known to prevent postoperative atrial fibrillation. However, the effectiveness of intraoperative landiolol on mortality remains unknown. This study aimed to evaluate the association between intraoperative landiolol use and the in-hospital mortality in patients undergoing CABG. METHODS: To conduct this retrospective cohort study, we used data from the Japanese Diagnosis Procedure Combination inpatient database. All patients who underwent CABG during hospitalization between July 1, 2010, and March 31, 2020, were included. Patients who received intraoperative landiolol were defined as the landiolol group, whereas the other patients were defined as the control group. The primary outcome was in-hospital mortality. Propensity score matching was used to compare the landiolol and control groups. RESULTS: In total, 118,506 patients were eligible for this study, including 25,219 (21%) in the landiolol group and 93,287 (79%) in the control group. One-to-one propensity score matching created 24,893 pairs. After propensity score matching, the in-hospital mortality was significantly lower in the landiolol group than that in the control group (3.7% vs 4.3%; odds ratio 0.85; 95% confidence interval 0.78 to 0.94; P = .010). CONCLUSIONS: Intraoperative landiolol use was associated with decreased in-hospital mortality in patients undergoing CABG. Further randomized controlled trials are required to confirm these findings.

Epidemiological analysis of Legionella pneumonia in Japan: A national inpatient database study.

BACKGROUND: Legionella pneumonia, a severe form of pneumonia, is caused by Legionella bacteria. The epidemiology of Legionnaires' disease in Japan, including seasonal trends, risk factors for severe disease, and fatality rates, is unclear. This study examined the epidemiology of Legionella pneumonia in Japan. METHODS: This retrospective cohort study included data of adult patients hospitalized for Legionella pneumonia (identified using the ICD-10 code, A481) in the Japanese Diagnosis Procedure Combination inpatient database, from April 2011 to March 2021. We performed multivariable logistic regression analysis to explore the prognostic factors of in-hospital mortality. RESULTS: Of 7370 enrolled hospitalized patients from 1140 hospitals (male, 84.4%; aged >50 years, 87.9%), 469 (6.4%) died during hospitalization. The number of hospitalized patients increased yearly, from 658 in 2016 to 975 in 2020. Multivariable logistic regression analysis revealed that higher in-hospital mortality was associated with older age, male sex, lower body mass index, worsened level of consciousness, comorbidities (congestive heart failure, chronic renal diseases, and metastasis), hospitalization from November to May, and ambulance use. However, lower in-hospital mortality was associated with comorbidity (liver diseases), hospitalization after 2013, and hospitalization in hospitals with higher case volume. CONCLUSIONS: The characterized epidemiology of Legionella pneumonia in Japan revealed a high mortality rate of 6.4%. To the best of our knowledge, this is the first study to demonstrate a higher mortality rate in winter and in patients with congestive heart failure and metastasis. Further research is needed to understand the complex interplay between the prognostic factors of Legionella pneumonia.