Mortality After Alcohol Septal Ablation vs. Septal Myectomy in Patients With Obstructive Hypertrophic Cardiomyopathy.

Background: Alcohol septal ablation (ASA) and septal myectomy (SM) are 2 options for septal reduction therapy (SRT) to treat medication-resistant symptomatic obstructive hypertrophic cardiomyopathy (HCM). Because differences in mortality rates after these different SRT methods have not been extensively investigated in real-world settings, in this study compared the 1-year mortality rates after ASA and SM using population-based database. Methods and Results: Utilizing New York Statewide Planning and Research Cooperative System (SPARCS) data from 2005 to 2016, we performed a comparative effectiveness study of ASA vs. SM in patients with HCM. The outcome was all-cause death up to 360 days after SRT. We constructed a multivariable logistic regression model and performed sensitivity analysis with propensity score (PS)-matching and inverse probability of treatment weighting (IPTW) methods. We identified 755 patients with HCM who underwent SRT: 348 with ASA and 407 with SM. The multivariable analysis showed that all-cause deaths were significantly fewer in the ASA group at 360 days after SRT (adjusted odds ratio=0.34; 95% confidence interval [CI] 0.13-0.84; P=0.02). The PS-matching and IPTW methods also supported a lower mortality rate in the ASA group at 360 days post-SRT. Conclusions: In this population-based study of patients with HCM who underwent SRT in a real-world setting, the 1-year all-cause mortality rate was significantly lower in patients who underwent ASA compared with SM.

Machine Learning Detects Heterogeneous Effects of Medicaid Coverage on Depression.

In 2008, Oregon expanded its Medicaid program using a lottery, creating a rare opportunity to study the effects of Medicaid coverage using a randomized controlled design (Oregon Health Insurance Experiment). Analysis showed that Medicaid coverage lowered the risk of depression. However, this effect may vary between individuals, and the identification of individuals likely to benefit the most has the potential to improve the effectiveness and efficiency of the Medicaid program. By applying the machine learning causal forest to data from this experiment, we found substantial heterogeneity in the effect of Medicaid coverage on depression; individuals with high predicted benefit were older and had more physical or mental health conditions at baseline. Expanding coverage to individuals with high predicted benefit generated greater reduction in depression prevalence than expanding to all eligible individuals (21.5 vs. 8.8 percentage point reduction; adjusted difference [95%CI], +12.7 [+4.6,+20.8]; P=0.003), at substantially lower cost per case prevented ($16,627 vs. $36,048; adjusted difference [95%CI], -$18,598 [-$156,953,-$3,120]; P=0.04). Medicaid coverage reduces depression substantially more in a subset of the population than others, in ways that are predictable in advance. Targeting coverage on those most likely to benefit could improve the effectiveness and efficiency of insurance expansion.

Trauma mechanisms and patterns of blunt cervical vascular injury: A descriptive study using a nationwide trauma registry.

OBJECTIVE: Blunt cervical vascular injury (BCVI) is a non-penetrating trauma to the carotid and/or vertebral vessels following a direct injury to the neck or by the shearing of the cervical vessels. Despite its potentially life-threatening nature, important clinical features of BCVI such as typical patterns of co-occurring injuries for each trauma mechanism are not well known. To address this knowledge gap, we described the characteristics of patients with BCVI to identify the pattern of co-occurring injuries by common trauma mechanisms. METHODS: This is a descriptive study using a Japanese nationwide trauma registry from 2004 through 2019. We included patients aged ≥13 years presenting to the emergency department (ED) with BCVI, defined as a blunt trauma to any of the following vessels: common/internal carotid artery, external carotid artery, vertebral artery, external jugular vein, and internal jugular vein. We delineated characteristics of each BCVI classified according to three damaged vessels (common/internal carotid artery, vertebral artery, and others). In addition, we applied network analysis to unravel patterns of co-occurring injuries among patients with BCVI by four common trauma mechanisms (car accident, motorcycle/bicycle accident, simple fall, and fall from a height). RESULTS: Among 311,692 patients who visited the ED for blunt trauma, 454 (0.1%) patients had BCVI. Patients with common/internal carotid artery injuries presented to the ED with severe symptoms (e.g., the median Glasgow Coma Scale was 7) and had high in-hospital mortality (45%), while patients with vertebral artery injuries presented with relatively stable vital signs. Network analysis showed that head-vertebral-cervical spine injuries were common across four trauma mechanisms (car accident, motorcycle/bicycle accident, simple fall, and fall from a height), with co-occurring injuries of the cervical spine and vertebral artery being the most common injuries due to falls. In addition, common/internal carotid artery injuries were associated with thoracic and abdominal injuries in patients with car accidents. CONCLUSIONS: Based on analyses of a nationwide trauma registry, we found that patients with BCVI had distinct patterns of co-occurring injuries by four trauma mechanisms. Our observations provide an important basis for the initial assessment of blunt trauma and could support the management of BCVI.

Targeted therapy using polymyxin B hemadsorption in patients with sepsis: a post-hoc analysis of the JSEPTIC-DIC study and the EUPHRATES trial.

BACKGROUND: Polymyxin B hemadsorption (PMX-HA) reduces blood endotoxin levels, but characteristics of patients with sepsis likely to benefit from PMX-HA are not well known. We sought to identify patient subgroups likely to benefit from PMX-HA. METHODS: We retrospectively identified 1911 patients with sepsis from a retrospective observational study in Japan (the JSEPTIC-DIC study) and 286 patients with endotoxemic septic shock from a randomized controlled trial in North America that restricted patients to those with high endotoxin activity (the EUPHRATES trial). We applied the machine learning-based causal forest model to the JSEPTIC-DIC cohort to investigate heterogeneity in treatment effects of PMX-HA on 28-day survival after adjusting for potential confounders and ascertain the best criteria for PMX-HA use. The derived criteria for targeted therapy by PMX-HA were validated using the EUPHRATES trial cohort. RESULTS: The causal forest model revealed heterogeneity in treatment effects of PMX-HA. Since patients having higher treatment effects were more likely to have severe coagulopathy and hyperlactatemia, we identified the potential treatment targets of PMX-HA as patients with PT-INR > 1.4 or lactate > 3 mmol/L. In the EUPHRATES trial cohort, PMX-HA use on the targeted subpopulation (75% of all patients) was significantly associated with higher 28-day survival (PMX-HA vs. control, 68% vs. 52%; treatment effect of PMX-HA, + 16% [95% CI + 2.2% to + 30%], p = 0.02). CONCLUSIONS: Abnormal coagulation and hyperlactatemia in septic patients with high endotoxin activity appear to be helpful to identify patients who may benefit most from PMX-HA. Our findings will inform enrollment criteria for future interventional trials targeting patients with coagulopathy and hyperlactatemia.

The Association Between Time From Emergency Department Visit to ICU Admission and Mortality in Patients With Sepsis.

The Surviving Sepsis Campaign Guidelines 2021 recommends that adult patients with sepsis requiring intensive care should be admitted to the ICU within 6 hours of their emergency department (ED) visits. However, there is limited evidence on whether 6 hours is the best target time for compliance with the sepsis bundle. We aimed to investigate the association between time from ED visits to ICU admission (i.e., ED length of stay [ED-LOS]) and mortality and identify the optimal ED-LOS for patients with sepsis. DESIGN: Retrospective cohort study. SETTING: The Medical Information Mart for Intensive Care Emergency Department and Medical Information Mart for Intensive Care IV databases. PATIENTS: Adult patients (≥ 18 yr old) who were transferred from the ED to the ICU and subsequently diagnosed with sepsis based on the Sepsis-3 criteria within 24 hours of ICU admission. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among 1,849 patients with sepsis, we found a disproportionally higher mortality rate in patients immediately admitted to the ICU (e.g., < 2 hr). When using ED-LOS as a continuous variable, ED-LOS was not significantly associated with 28-day mortality (adjusted odds ratio [OR] per hour increase, 1.04; 95% CI, 0.96-1.13; p = 0.3) after an adjustment for potential confounders (e.g., demographics, triage vital signs, and laboratory results) in the multivariable analysis. However, when we categorized all patients into time quartiles (ED-LOS: < 3.3 hr, 3.3-4.5 hr, 4.6-6.1 hr, and > 6.1 hr), patients in the higher time quartiles (e.g., 3.3-4.5 hr) had higher 28-day mortality compared with those in the lowest time quartile (< 3.3 hr) (e.g., adjusted OR for patients in the second time quartile [3.3-4.5 hr] 1.59; 95% CI, 1.03-2.46; p = 0.04). CONCLUSIONS: Earlier admission to the ICU (e.g., within 3.3 hr of ED visits) was associated with lower 28-day mortality in patients with sepsis. Our findings suggest patients with sepsis who require intensive care may benefit from a more immediate ICU admission than 6 hours.

Monitoring the Resolution of Acute Exacerbation of Airway Bronchoconstriction in an Asthma Attack Using Capnogram Waveforms.

Patients with acute bronchospasm can show a distinct slope of the capnogram ("shark fin") as a result of asynchronous alveolar excretion. Although the slope of the upward alveolar plateau (phase III) in the capnogram waveforms of non-intubated patients is known to help monitor the therapeutic response to acute bronchospasm, little is known about the significance of its slope among intubated patients. Therefore, we quantified the phase III slope of an intubated patient with acute asthma to investigate whether capnogram waveforms could be useful for identifying the response to antibronchospasm treatment in real time. CASE SUMMARY: The patient was a 53-year-old man who had a history of asthma. He presented to the emergency department with the primary complaint of respiratory distress. He was diagnosed with severe asthma attack and required invasive mechanical ventilation for 10 days, during which we quantified the phase III slope of the capnogram. The phase III slope decreased during treatment, with a significant reduction from the third to the fourth day; however, a significant decrease in end-tidal carbon dioxide (EtCO2) was observed from the fifth to the sixth day. We found that the slope values decreased earlier than EtCO2 reduction, although the absolute EtCO2 values eventually decreased in response to antibronchospasm treatment. CONCLUSION: There were several reports that evaluated the phase III slope in non-intubated patients with asthma, but this is the first report measuring the phase III slope in an intubated patient over several days. Capnogram waveforms may serve as useful real-time indicators to monitor acute bronchospasm among mechanically ventilated patients.

The prognostic utility of prehospital qSOFA in addition to emergency department qSOFA for sepsis in patients with suspected infection: A retrospective cohort study.

BACKGROUND: The quick sequential organ failure assessment (qSOFA) was widely used to estimate the risks of sepsis in patients with suspected infection in the prehospital and emergency department (ED) settings. Due to the insufficient sensitivity of qSOFA on arrival at the ED (ED qSOFA), the Surviving Sepsis Campaign 2021 recommended against using qSOFA as a single screening tool for sepsis. However, it remains unclear whether the combined use of prehospital and ED qSOFA improves its sensitivity for identifying patients at a higher risk of sepsis at the ED. METHODS: We retrospectively analyzed the data from the ED of a tertiary medical center in Japan from April 2018 through March 2021. Among all adult patients (aged ≥18 years) transported by ambulance to the ED with suspected infection, we identified patients who were subsequently diagnosed with sepsis based on the Sepsis-3 criteria. We compared the predictive abilities of prehospital qSOFA, ED qSOFA, and the sum of prehospital and ED qSOFA (combined qSOFA) for sepsis in patients with suspected infection at the ED. RESULTS: Among 2,407 patients with suspected infection transported to the ED by ambulance, 369 (15%) patients were subsequently diagnosed with sepsis, and 217 (9%) died during hospitalization. The sensitivity of prehospital qSOFA ≥2 and ED qSOFA ≥2 were comparable (c-statistics for sepsis [95%CI], 0.57 [0.52-0.62] vs. 0.55 [0.50-0.60]). However, combined qSOFA (cutoff, ≥3 [max 6]) was more sensitive than ED qSOFA (cutoff, ≥2) for identifying sepsis (0.67 [95%CI, 0.62-0.72] vs. 0.55 [95%CI, 0.50-0.60]). Using combined qSOFA, we identified 44 (12%) out of 369 patients who were subsequently diagnosed with sepsis, which would have been missed using ED qSOFA alone. CONCLUSIONS: Using both prehospital and ED qSOFA could improve the screening ability of sepsis among patients with suspected infection at the ED.

Machine-learning approaches to identify determining factors of happiness during the COVID-19 pandemic: retrospective cohort study.

OBJECTIVE: To investigate determining factors of happiness during the COVID-19 pandemic. DESIGN: Observational study. SETTING: Large online surveys in Japan before and during the COVID-19 pandemic. PARTICIPANTS: A random sample of 25 482 individuals who are representatives of the Japanese population. MAIN OUTCOME MEASURE: Self-reported happiness measured using a 10-point Likert scale, where higher scores indicated higher levels of happiness. We defined participants with ≥8 on the scale as having high levels of happiness. RESULTS: Among the 25 482 respondents, the median score of self-reported happiness was 7 (IQR 6-8), with 11 418 (45%) reporting high levels of happiness during the pandemic. The multivariable logistic regression model showed that meaning in life, having a spouse, trust in neighbours and female gender were positively associated with happiness (eg, adjusted OR (aOR) for meaning in life 4.17; 95% CI 3.92 to 4.43; p<0.001). Conversely, self-reported poor health, anxiety about future household income, psychiatric diseases except depression and feeling isolated were negatively associated with happiness (eg, aOR for self-reported poor health 0.44; 95% CI 0.39 to 0.48; p<0.001). Using machine-learning methods, we found that meaning in life and social capital (eg, having a spouse and trust in communities) were the strongest positive determinants of happiness, whereas poor health, anxiety about future household income and feeling isolated were important negative determinants of happiness. Among 6965 subjects who responded to questionnaires both before and during the COVID-19 pandemic, there was no systemic difference in the patterns as to determinants of declined happiness during the pandemic. CONCLUSION: Using machine-learning methods on data from large online surveys in Japan, we found that interventions that have a positive impact on social capital as well as successful pandemic control and economic stimuli may effectively improve the population-level psychological well-being during the COVID-19 pandemic.

The Contribution of Chest X-Ray to Predict Extubation Failure in Mechanically Ventilated Patients Using Machine Learning-Based Algorithms.

OBJECTIVES: To evaluate the contribution of a preextubation chest X-ray (CXR) to identify the risk of extubation failure in mechanically ventilated patients. DESIGN: Retrospective cohort study. SETTINGS: ICUs in a tertiary center (the Medical Information Mart for Intensive Care IV database). PATIENTS: Patients greater than or equal to 18 years old who were mechanically ventilated and extubated after a spontaneous breathing trial. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among 1,066 mechanically ventilated patients, 132 patients (12%) experienced extubation failure, defined as reintubation or death within 48 hours of extubation. To predict extubation failure, we developed the following models based on deep learning (EfficientNet) and machine learning (LightGBM) with the training data: 1) model using only the rapid-shallow breathing index (RSBI), 2) model using RSBI and CXR, 3) model using all candidate clinical predictors (i.e., patient demographics, vital signs, laboratory values, and ventilator settings) other than CXR, and 4) model using all candidate clinical predictors with CXR. We compared the predictive abilities between models with the test data to investigate the predictive contribution of CXR. The predictive ability of the model using CXR as well as RSBI was not significantly higher than that of the model using only RSBI (c-statistics, 0.56 vs 0.56; p = 0.95). The predictive ability of the model using clinical predictors with CXR was not significantly higher than that of the model using all clinical predictors other than CXR (c-statistics, 0.71 vs 0.70; p = 0.12). Based on SHapley Additive exPlanations values to interpret the model using all clinical predictors with CXR, CXR was less likely to contribute to the predictive ability than other predictors (e.g., duration of mechanical ventilation, inability to follow commands, and heart rate). CONCLUSIONS: Adding CXR to a set of other clinical predictors in our prediction model did not significantly improve the predictive ability of extubation failure in mechanically ventilated patients.

Risk factors of sepsis among patients with qSOFA<2 in the emergency department.

OBJECTIVE: Studies have suggested that qSOFA can be used for early detection of sepsis immediately upon arrival at the emergency department (ED). Despite this, little is known about the risk factors associated with the subsequent diagnosis of sepsis among patients with qSOFA<2 in the ED. METHODS: This is a retrospective cohort study using ED data from a large tertiary medical center in Japan, 2018-2020. We included adult patients (aged ≥18 years) presenting to the ED with suspected infection (e.g., having a fever) and qSOFA<2. We identified patients who developed sepsis based on the Sepsis-3 criteria, and compared patient characteristics (e.g., demographics, vital signs upon the initial triage, chief complaint, and comorbidities) between patients who developed sepsis or not. Additionally, we identified the potential risk factors of sepsis among patients with qSOFA<2 using a multivariable logistic regression model. RESULTS: We identified 151 (7%) patients who developed sepsis among 2025 adult patients with suspected infection and qSOFA<2. Compared with patients who did not develop sepsis, patients who developed sepsis were likely to be older and have vital signs suggestive of imminent sepsis (e.g., high respiratory rate). In the multivariable logistic regression model, the potential risk factors of sepsis among patients with qSOFA<2 were older age (adjusted OR, 1.92 [95%CI 1.19-3.19]), vital signs suggestive of imminent sepsis (e.g., adjusted OR of altered mental status, 3.50 [95%CI 2.25-5.50]), receipt of oxygen therapy upon arrival at the ED (adjusted OR, 1.91 [95%CI 1.38-2.26]), chief complaint of sore throat (adjusted OR, 2.15 [95%CI 1.08-4.13]), and the presence of comorbid diabetes mellitus, ischemic heart disease, and chronic kidney disease (e.g., adjusted OR of diabetes mellitus, 1.47 [95%CI 1.10-1.96]). On the contrary, chief complaint of abdominal and chest pain were associated with a lower risk of sepsis (e.g., adjusted OR of abdominal pain, 0.26 [95%CI 0.14-0.45]). CONCLUSIONS: We found that older age, vital signs prognosticating sepsis, and the presence of some comorbidities were the potential risk factors of sepsis in patients with qSOFA<2. These potential risk factors could be useful to efficiently recognize patients who might develop sepsis in the ED.

Physician visits and medication prescriptions for major chronic diseases during the COVID-19 pandemic in Japan: retrospective cohort study.

OBJECTIVES: There have been concerns that patients with chronic conditions may be avoiding in-person physician visits due to fear of COVID-19, leading to lower quality of care. We aimed to investigate changes in physician visits and medication prescriptions for chronic diseases before and during the COVID-19 pandemic at the population level. DESIGN: Retrospective cohort study. SETTING: Nationwide claims data in Japan, 2018-2020. PARTICIPANTS: Working-age population (aged 18-74 years) who visited physicians and received any prescriptions for major chronic diseases (hypertension, diabetes and dyslipidaemia) before the pandemic. OUTCOME MEASURES: The outcomes were the monthly number of physician visits, the monthly proportion of physician visits and the monthly proportion of days covered by prescribed medication (PDC) during the pandemic (April-May 2020, as the first state of emergency over COVID-19 was declared on 7 April, and withdrawn nationally on 25 May). RESULTS: Among 10 346 patients who visited physicians for chronic diseases before the pandemic, we found a temporary decline in physician visits (mean number of visits was 1.9 in March vs 1.7 in April; p<0.001) and an increase in the proportion of patients who did not visit any physicians during the pandemic (15% in March vs 24% in April; p<0.001). Physician visits returned to the baseline in May (the mean number of visits: 1.8, and the proportion of patients who did not visit any physicians: 9%). We observed no clinically meaningful difference in PDC between before and during the pandemic (eg, 87% in March vs 87% in April; p=0.45). A temporary decline in physician visits was more salient in seven prefectures with a larger number of COVID-19 cases than in other areas. CONCLUSIONS: Although the number of physician visits declined right after the COVID-19 outbreak, it returned to the baseline one month later; patients were not skipping medications during the pandemic.

Clinical performance of early warning scoring systems for identifying sepsis among anti-hypertensive agent users.

BACKGROUND: Little is known about the accuracy of the quick Sequential Organ Failure Assessment (qSOFA) and the National Early Warning Score (NEWS) in identifying sepsis patients with a history of hypertension on anti-hypertensive agents, which affect vital signs as components of the scoring systems. We aimed to examine the ability of qSOFA and NEWS to predict sepsis among anti-hypertensive agent users by comparing them with non-users. METHODS: We retrospectively identified adult patients (aged ≥18years) with suspected infection who presented to an emergency department (ED) of a large tertiary medical center in Japan between April 2018 and March 2020. Suspected infection was defined based on the chief complaint of fever, high body temperature, or the clinical context on arrival at the ED. We excluded patients who had trauma or cardiac arrest, those who were transported to other hospitals after arrival at the ED, and those whose vital signs data were mostly missing. The predictive performances of qSOFA and NEWS based on initial vital signs were examined separately for sepsis, ICU admission, and in-hospital mortality and compared between anti-hypertensive agent users and non-users. RESULTS: Among 2900 patients with suspected infection presenting to the ED, 291 (10%) had sepsis, 1023 (35%) were admitted to the ICU, and 188 (6.5%) died. The prediction performances of qSOFA and NEWS for each outcome among anti-hypertensive agent users were lower than that among non-users (e.g., c-statistics of qSOFA for sepsis, 0.66 vs. 0.71, p = 0.07; and for ICU admission, 0.70 vs. 0.75, p = 0.01). For identifying sepsis, the sensitivity and specificity of qSOFA ≥2 were 0.43 and 0.77 in anti-hypertensive agent users and 0.51 and 0.82 in non-users. Similar associations were observed for identifying ICU admission and in-hospital mortality. Regardless of the use of anti-hypertensive agents, NEWS had better prediction abilities for each outcome than qSOFA. CONCLUSION: The clinical performance of qSOFA and NEWS for identifying sepsis among anti-hypertensive agent users was likely lower than that among non-users.

Dynamic changes in fibrinogen and D-dimer levels in COVID-19 patients on nafamostat mesylate.

Critical illnesses associated with coronavirus disease 2019 (COVID-19) are attributable to a hypercoagulable status. There is limited knowledge regarding the dynamic changes in coagulation factors among COVID-19 patients on nafamostat mesylate, a potential therapeutic anticoagulant for COVID-19. First, we retrospectively conducted a cluster analysis based on clinical characteristics on admission to identify latent subgroups among fifteen patients with COVID-19 on nafamostat mesylate at the University of Tokyo Hospital, Japan, between April 6 and May 31, 2020. Next, we delineated the characteristics of all patients as well as COVID-19-patient subgroups and compared dynamic changes in coagulation factors among each subgroup. The subsequent dynamic changes in fibrinogen and D-dimer levels were presented graphically. All COVID-19 patients　were classified into three subgroups: clusters A, B, and C, representing low, intermediate, and high risk of poor outcomes, respectively. All patients were alive 30 days from symptom onset. No patient in cluster A required mechanical ventilation; however, all patients in cluster C required mechanical ventilation, and half of them were treated with venovenous extracorporeal membrane oxygenation. All patients in cluster A maintained low D-dimer levels, but some critical patients in clusters B and C showed dynamic changes in fibrinogen and D-dimer levels. Although the potential of nafamostat mesylate needs to be evaluated in randomized clinical trials, admission characteristics of patients with COVID-19 could predict subsequent coagulopathy.

Machine-learning-based prediction models for high-need high-cost patients using nationwide clinical and claims data.

High-need, high-cost (HNHC) patients-usually defined as those who account for the top 5% of annual healthcare costs-use as much as half of the total healthcare costs. Accurately predicting future HNHC patients and designing targeted interventions for them has the potential to effectively control rapidly growing healthcare expenditures. To achieve this goal, we used a nationally representative random sample of the working-age population who underwent a screening program in Japan in 2013-2016, and developed five machine-learning-based prediction models for HNHC patients in the subsequent year. Predictors include demographics, blood pressure, laboratory tests (e.g., HbA1c, LDL-C, and AST), survey responses (e.g., smoking status, medications, and past medical history), and annual healthcare cost in the prior year. Our prediction models for HNHC patients combining clinical data from the national screening program with claims data showed a c-statistics of 0.84 (95%CI, 0.83-0.86), and overperformed traditional prediction models relying only on claims data.

Characteristics and subgroups of frequent emergency department users in an academic hospital in Japan.

AIM: Frequent emergency department (ED) users increase the burden on EDs. However, little is known about the characteristics and subgroups of frequent ED users in Japan. METHODS: We retrospectively analyzed data on patients who had visited the ED of an academic hospital in Japan between 2014 and 2015. We identified adult frequent ED users (four or more ED visits within 365 days prior to one's last visit) and sampled adult non-frequent ED users. We compared these groups to delineate the characteristics of frequent ED users and examined the association between frequent ED use and hospitalization rates. Additionally, to identify latent subgroups of frequent ED users, we undertook a cluster analysis. RESULTS: We identified 259 frequent ED users and 297 non-frequent ED users from 9,546 patients who had visited the ED in 2015. Frequent ED users accounted for 8.2% of all ED visits. Frequent ED users tended to be older, have comorbidities, and be receiving public assistance compared to non-frequent ED users. There was a significant association between frequent ED use and higher hospitalization rates, which was partially attributable to (older) age and comorbidities. In the cluster analysis, we identified four subgroups of frequent ED users: (i) older patients with malignant tumors and the highest hospitalization rates, (ii) patients with mental illnesses and the lowest hospitalization rates, (iii) patients who were at risk of cardiovascular diseases, (iv) others. CONCLUSIONS: Frequent ED users tended to be older and have comorbidities. Four latent subgroups of frequent ED users were identified.