Objectives To compare baseline, cluster-based and trajectory-based classifications of continuity of primary care (COC) and to examine their associations with chronic obstructive pulmonary disease (COPD)-related hospitalisation and emergency department (ED) visits.Design Population-based retrospective cohort study.Setting National Health Insurance claims data from South Korea (Korean National Health Insurance Service), 2014–2021.Participants 92 977 patients aged ≥40 years newly diagnosed with COPD between 2015 and 2016, with at least four ambulatory primary care visits during the exposure period.Primary and secondary outcome measures: The primary outcome was the incidence of COPD-related hospitalisation; the secondary outcome was the incidence of COPD-related ED visits. Continuity of primary care was quantified using the Continuity of Care Index (COCI) and classified using three approaches: (1) a baseline COCI-based method, (2) a cluster-based method using K-means clustering and (3) a trajectory-based method using group-based trajectory modelling. Fine-Gray subdistribution hazard models, accounting for death as a competing risk, were used to estimate adjusted HRs (aHRs).Results Across all three classification approaches, low continuity of care was consistently associated with an increased risk of COPD-related hospitalisation (aHR 2.43, 95% CI 2.22 to 2.66 for baseline COCI; 2.26, 95% CI 2.06 to 2.47 for cluster-based; 2.73, 95% CI 2.49 to 2.99 for trajectory-based) and ED visits (aHR 2.32, 95% CI 2.04 to 2.63 for baseline COCI; 2.55, 95% CI 2.25 to 2.88 for cluster-based; 3.48, 95% CI 3.05 to 3.96 for trajectory-based). Effect estimates were consistently strongest for the trajectory-based approach and weakest for the baseline COCI approach. Agreement among the three classification methods was substantial (overall 87.2%; Fleiss’ kappa 0.78).Conclusions Baseline COCI classification offers a pragmatic and robust measure of COC, producing effect estimates directionally consistent with those derived from more complex longitudinal approaches; however, observed transitions between continuity groups over time indicate that reliance on baseline classification alone may attenuate effect estimates when continuity patterns change. Trajectory-based methods may yield additional insight in populations with greater temporal variability in care patterns but entail substantially higher data and modelling requirements.

OBJECTIVES:This study aimed to estimate the incidence of adverse pregnancy outcomes (APO) in patients with systemic lupus erythematosus (SLE) and to evaluate the risks associated with immunosuppressant use-including hydroxychloroquine and teratogenic agents such as mycophenolate mofetil, methotrexate and cyclophosphamide-across specific APO categories. METHODS:A cohort study was conducted using the 2005-2018 National Health Information Database of the National Health Insurance Service in Korea, involving 4,880 pregnancies in 3,059 women with SLE. The incidences of preeclampsia/eclampsia, preterm birth, spontaneous abortion and stillbirth were estimated. Associations between APOs and medication patterns from preconception through pregnancy were analysed using univariate and multivariable models. RESULTS:The overall APO incidence among pregnant women with SLE was 45.0% (95% CI: 43.4, 46.5%). Compared with continuous hydroxychloroquine use, non-use (adjusted odds ratio [AOR]: 1.39; 95% CI: 1.05, 1.85), discontinuation (AOR: 2.18; 95% CI: 1.61, 2.95), and initiation during pregnancy (AOR: 2.17; 95% CI: 1.16, 4.06) were significantly associated with increased preterm birth risk. Exposure to teratogenic immunosuppressants within 3 months of preconception or during the first trimester was associated with increased spontaneous abortion risk (AOR: 2.59 and 3.18, respectively). CONCLUSION:Continuity of hydroxychloroquine use from preconception through pregnancy reduces preterm birth risk in SLE. Conversely, early exposure to teratogenic immunosuppressants heightens the risk of spontaneous abortion. These findings underscore the importance of preconception medication planning in women with SLE.

Longitudinal zero-inflated count data frequently arise in various fields such as medicine and social sciences. Standard hurdle models separate zero and positive counts, but fail to directly infer marginal means, limiting their ability to assess overall covariate effects. This paper introduces overall marginalized hurdle random effects models (OMHREMs) for zero-inflated count data, which extends the traditional hurdle model by directly modeling the marginal mean while considering random effects to account for heterogeneity. OMHREMs enable population-average effects of covariates like odds ratio, providing how covariates influence the overall mean in zero-inflated count data. Through simulation studies, we evaluate the performance of OMHREMs. Furthermore, we apply our approach to systemic lupus erythematosus data to compare its effectiveness against existing models.

Linear models commonly used in longitudinal data analysis often assume a multivariate normal distribution. This assumption, however, can lead to biased mean parameter estimates in the presence of outliers. To address this, alternative linear models based on multivariate t distributions have been developed. In this paper, we review the commonly used multivariate distributions applicable to multivariate longitudinal data and introduce multivariate Laplace linear models (MLLMs) that are designed to handle outliers effectively. These models incorporate a scale matrix that is autoregressive, heteroscedastic, and positive definite, using modified Cholesky and hypersphere decompositions. We conduct simulation studies and apply these models to a real data example, comparing the performance of MLLMs with multivariate normal linear models (MNLMs) and multivariate t linear models (MTLMs), and providing insights on when each model is most appropriate.

Background: Systemic Lupus Erythematosus (SLE) is a multifaceted autoimmune disorder characterized by diverse clinical manifestations. Despite improved survival rates, the mortality risk in SLE patients remains elevated compared to the general population. Objectives: We aimed to evaluate all-cause and cause-specific mortality risks in Korean patients with SLE, stratified by age and gender. Additionally, the impact of medications and comorbidities on mortality risk was investigated. Methods: Using data from the National Health Insurance database spanning 2008 to 2018, incident SLE patients aged 10-79 years were included. The primary endpoint was all-cause death and cause-specific death, with secondary outcomes focusing on cause-specific death stratified by age group. The main causes of death were identified using the ICD-10 code of the primary diagnosis within six months prior to death. The mortality rate (MR) was calculated as the number of deaths per 100,000 person-years (PYs). A generalized estimating equations model was employed for risk factor analysis. Results: A total of 11,375 incident SLE patients were recruited, with an average age of 42.3 ± 16.7 years and 86.1% female. During 57,658 PYs of observation, 728 deaths occurred, resulting in an MR of 1,262.62 per 100,000 PYs. The MR for males (2,718.86/100,000 PYs) exceeded that for females (1,060.57/100,000 PYs). SLE itself (381.56/100,000 PYs) was the leading cause of death, followed by cardiovascular disease (202.92/100,000 PYs), cancer (175.17/100,000 PYs), infection (143.95/100,000 PYs), and renal disease (57.23/100,000 PYs). Age-specific mortality risk increased proportionally with both age and mortality risk. Among adolescents (10-19 years), all-cause MR was 520.47 per 100,000 PYs, with SLE itself accounting for over half of the cause of deaths. In elderly patients (70-79 years), all-cause mortality peaked at 7,252.06 per 100,000 PYs, emphasizing the impact of infection and cancer. Risk factor analysis for SLE-related mortality revealed significant associations with comorbidities (Table 2). Pulmonary alveolar hemorrhage (Hazard Ratio [HR] 9.93, 95% CI 3.81-25.89), pulmonary arterial hypertension (HR 3.77, 95% CI 1.54-9.21), and interstitial lung disease (HR 3.27, 95% CI 1.87-5.72) were identified as associated factors for mortality in Korean SLE patients. Medications were also associated with increased mortality risk; intravenous glucocorticoids (HR 16.38, 95% CI 10.06-26.66) and cyclophosphamide (HR 5.51, 95% CI 3.38-8.97) were linked to mortality risk in SLE. Conclusion: This study offers a comprehensive analysis of the mortality patterns in Korean SLE patients. SLE itself, cardiovascular disease, cancer, and infection emerged as the primary causes of death, with age at onset influencing mortality patterns. Pulmonary manifestations, intravenous glucocorticoids, and cyclophosphamide were significantly associated with an increased risk of mortality REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.

To analyze longitudinal zero-inflated count data, we extend existing models by introducing marginalized zero-inflated Poisson (MZIP) models with random effects, which explicitly capture the marginal effect of covariates and address limitations of previous methods. These models provide a clearer interpretation of the overall mean effect of covariates on zero-inflated count data. To further accommodate overdispersion, we develop marginalized zero-inflated negative binomial (MZINB) models. Both models incorporate subject-specific heterogeneity through a flexible random effects covariance structure. Simulation studies are conducted to evaluate the performance of the MZIP and MZINB models, comparing their inference under both homogeneous and heterogeneous random effects. Finally, we illustrate the applicability of the proposed models through an analysis of systemic lupus erythematosus data.

OBJECTIVE:Hospitalization often indicates deteriorating health, longer treatment times, and higher healthcare costs. This study aimed to investigate associations between continuity of care (COC) and asthma-related hospitalizations using a rigorous methodology. METHODS:This retrospective cohort study was conducted using national health insurance claims data. The study included adults with a diagnosis of asthma between 2015 and 2016 in a primary care setting. The exposure was measured using continuity of care indices (COCIs) during the first two years after inclusion. Cohorts were categorized into two groups based on COCI levels. The primary outcome was the incidence of asthma-related hospitalizations, and the secondary outcomes were emergency department (ED) utilization, systemic corticosteroid use, and asthma-related medical costs. RESULTS:A total of 24,173 patients were eligible for analysis, 13,212 of whom were continuously cared for by primary doctors (the continuity group), and 10,961 non-continuously (the non-continuity group). During a 2 year-follow-up period, 230 patients (1.74%) were hospitalized in the continuity group and 404 (3.69%) in the non-continuity group. After adjusting for confounding covariates, patients in the non-continuity group were found to be at significantly higher risk of hospital admission (adjusted hazard ratio (aHR)=2.04 [95% confidence interval = 1.73 ~ 2.41]). In addition, the risk of ED visits, systemic corticosteroid use, and costs were higher for patients in the non-continuity group (aHR = 2.26 [1.32 ~ 3.87], adjusted OR=1.58 [1.35 ~ 1.82], and expβ = 1.41 [1.37 ~ 1.45], respectively). CONCLUSIONS:In adult asthma patients at the early stages of illness, increased continuity of primary care was found to be associated with fewer hospitalizations, fewer ED visits, and lower healthcare expenditures.

To investigate cancer incidence and the potential influence of immunosuppressive agents in Korean systemic lupus erythematosus (SLE) patients. We conducted a retrospective analysis utilizing data from the Korea Healthcare Bigdata Linked Platform, which integrated the National Central Cancer Registry and National Health Insurance Service databases covering the period 2008–2017. Incidence rates (IRs) per 10,000 person-years (PYs) for site-specific cancers of SLE patients were calculated using ICD-O-3 codes. Multivariable logistic regression analysis was utilized to assess the association between immunosuppressive agents and cancer development in SLE patients. A total of 10,013 predominantly female (91

Background To evaluate the mortality patterns of SLE and the associated risk factors in Koreans.Methods Using the National Health Insurance database spanning 2008 to 2018, incident cases of SLE in patients aged 10–79 years were included. We analysed the all-cause mortality and cause-specific mortality, stratifying by sex and age. The mortality rate (MR) was calculated as the number of deaths per 100 000 person-years (PYs). The causes of death were identified by the International Classification of Diseases, 10th Revision codes during hospitalisation or emergency visit prior to death. A generalised estimating equation model was employed for risk factor analysis.Results In total, 11 375 incident SLE cases among patients with an average age of 42.3±16.7 years were recruited (86.1% female). During 57 658 PYs, 728 deaths occurred (MR 1262.62/100 000 PYs). The MR among men (2718.86/100 000 PYs) exceeded that among women (1060.57/100 000 PYs). The leading causes of death were SLE-related conditions (381.56/100 000 PYs), cardiovascular disease (CVD) (202.92/100 000 PYs), cancer (175.17/100 000 PYs) and infection (143.95/100 000 PYs). Of the SLE-related mortality, the key risk factors were pulmonary complications, such as pulmonary alveolar haemorrhage (OR 9.93), pulmonary arterial hypertension (OR 3.77) and interstitial lung disease (OR 3.27).Conclusions Among Korean patients with SLE, SLE-related conditions were the leading causes of mortality. However, CVD and cancer were also identified as the main causes of mortality. Furthermore, pulmonary manifestations were significantly associated with SLE-related mortality.

To evaluate the incidence and risk of cardiovascular disease (CVD) among Korean patients with systemic lupus erythematosus (SLE) comparing them to diabetes patients and the general population. This nationwide cohort study focused on incident SLE patients aged over 40 years, matched with diabetes patients and the general population (1:4:4 ratio). CVD was defined as ischaemic heart disease, ischaemic stroke, and cardiac arrest. Incidence rate and incidence rate ratio (IRR) of CVD were calculated using generalised estimating equation models. The Fine-Gray model assessed risk factors for CVD in both SLE and diabetes patients. The study included 4272 incident SLE patients, 17,003 diabetes patients, and 17,088 from the general population. SLE patients had higher CVD risk compared to the general population, with adjusted IRRs of 1.99 for overall CVD. Diabetes patients showed increased CVD risk, but to a lesser extent, with an IRR of 1.39. SLE patients aged 40-59 years displayed a significantly elevated CVD risk. Advanced age, male gender, and current use of glucocorticoids, immunosuppressive, and anti-platelet agents were associated with increased CVD risk in SLE patients. SLE patients have a higher risk of CVD compared to the general population, more so than diabetes patients.

Objective: To validate algorithms for classifying disease activity in patients with systemic lupus erythematosus (SLE) using Korean claims data. Methods: We used data from a prospective cohort of SLE patients enrolled at a single academic center between October 2014 and August 2020. Disease activity was assessed at each visit using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K), with the annual average score serving as the gold standard. Three claims-based algorithms incorporating diagnostic codes for comorbidities and medication use were evaluated: (1) a previously established model including SLE-related comorbidities, immunosuppressants, and oral glucocorticoids, (2) a modified version incorporating intravenous glucocorticoids, and (3) a version with adjusted glucocorticoid dosage criteria (5 mg) to better identify mild to moderate disease. The performance of each algorithm in classifying mild disease activity—defined as SLEDAI-2K <3—was assessed by calculating sensitivity, specificity, positive predictive value (PPV), negative predictive value, and the area under the curve. Results: A total of 151 patients were included. The mean age was 34.5±8.7 years, and 94.7% were female. The mean initial SLEDAI-2K score was 3.6±2.6. The PPV for identifying mild disease activity ranged from 75.9% to 77.2%, with Algorithm 3 demonstrating the highest PPV. However, incorporating intravenous glucocorticoids or adjusting dosage thresholds did not result in further improvement. Conclusion: A claims-based algorithm using diagnostic and medication codes demonstrated a PPV of 77.2% for classifying mild disease activity in SLE. This approach may offer a practical method for disease activity assessment in Korean claims-based research.

OBJECTIVES:This study developed an algorithm for identifying pregnancy episodes and estimating the last menstrual period (LMP) in an administrative claims database and applied it to investigate the use of pregnancy-incompatible immunosuppressants among pregnant women with systemic lupus erythematosus (SLE).METHODS:An algorithm was developed and applied to a nationwide claims database in Korea. Pregnancy episodes were identified using a hierarchy of pregnancy outcomes and clinically plausible periods for subsequent episodes. The LMP was estimated using preterm delivery, sonography, and abortion procedure codes. Otherwise, outcome-specific estimates were applied, assigning a fixed gestational age to the corresponding pregnancy outcome. The algorithm was used to examine the prevalence of pregnancies and utilization of pregnancy-incompatible immunosuppressants (cyclophosphamide [CYC]/mycophenolate mofetil [MMF]/methotrexate [MTX]) and non-steroidal anti-inflammatory drugs (NSAIDs) during pregnancy in SLE patients.RESULTS:The pregnancy outcomes identified in SLE patients included live births (67%), stillbirths (2%), and abortions (31%). The LMP was mostly estimated with outcome-specific estimates for full-term births (92.3%) and using sonography procedure codes (54.7%) and preterm delivery diagnosis codes (37.9%) for preterm births. The use of CYC/MMF/MTX decreased from 7.6% during preconception to 0.2% at the end of pregnancy. CYC/MMF/MTX use was observed in 3.6% of women within 3 months preconception and 2.5% during 0-7 weeks of pregnancy.CONCLUSIONS:This study presents the first pregnancy algorithm using a Korean administrative claims database. Although further validation is necessary, this study provides a foundation for evaluating the safety of medications during pregnancy using secondary databases in Korea, especially for rare diseases.

Analysis of healthcare utilization, such as hospitalization duration and medical costs, is crucial for policymakers and doctors in experimental and epidemiological investigations. Herein, we examine the healthcare utilization data of patients with systemic lupus erythematosus (SLE). The characteristics of the SLE data were measured over a 10-year period with outliers. Multivariate linear models with multivariate normal error distributions are commonly used to evaluate long series of multivariate longitudinal data. However, when there are outliers or heavy tails in the data, such as those based on healthcare utilization, the assumption of multivariate normality may be too strong, resulting in biased estimates. To address this, we propose multivariate t-linear models (MTLMs) with an autoregressive moving-average (ARMA) covariance matrix. Modeling the covariance matrix for multivariate longitudinal data is difficult since the covariance matrix is high dimensional and must be positive-definite. To address these, we employ a modified ARMA Cholesky decomposition and hypersphere decomposition. Several simulation studies are conducted to demonstrate the performance, robustness, and flexibility of the proposed models. The proposed MTLMs with ARMA structured covariance matrix are applied to analyze the healthcare utilization data of patients with SLE.

Background Chronic comorbid conditions are common in patients with sepsis and may affect the outcomes. This study aimed to evaluate the prevalence and outcomes of common comorbidities in patients with sepsis. Methods We conducted a nationwide retrospective cohort study. Using data from the National Health Insurance Service of Korea. Adult patients (age ≥ 18 years) who were hospitalized in tertiary or general hospitals with a diagnosis of sepsis between 2011 and 2016 were analyzed. After screening of all International Classification of Diseases 10th revision codes for comorbidities, we identified hypertension, diabetes mellitus (DM), liver cirrhosis (LC), chronic kidney disease (CKD), and malignancy as prevalent comorbidities. Results Overall, 373,539 patients diagnosed with sepsis were hospitalized in Korea between 2011 and 2016. Among them, 46.7% had hypertension, 23.6% had DM, 7.4% had LC, 13.7% had CKD, and 30.7% had malignancy. In-hospital mortality rates for patients with hypertension, DM, LC, CKD, and malignancy were 25.5%, 25.2%, 34.5%, 28.0%, and 33.3%, respectively, showing a decreasing trend over time ( P < 0.001). After adjusting for baseline characteristics, male sex, older age, use of mechanical ventilation, and continuous renal replacement therapy, LC, CKD, and malignancy were significantly associated with in-hospital mortality. Conclusions Hypertension is the most prevalent comorbidity in patients with sepsis, and it is associated with an increased survival rate. Additionally, liver cirrhosis, chronic kidney disease, and malignancy result in higher mortality rates than hypertension and DM, and are significant risk factors for in-hospital mortality in patients with sepsis.

Objective This study aimed to investigate the impacts of continuity of care (COC) between patients and multiple providers, i.e., doctors and community pharmacists, on clinical and economic outcomes. Methods This is a retrospective cohort study and analyzed Korean national claims data for ambulatory care setting between 2007 and 2018. Patients with dyslipidemia newly diagnosed in 2008 were identified. COC between providers and patients was computed using the continuity of care index (COCI). Based on COCIs, the study patients were allocated to four groups: HM/HP, HM/LP, LM/HP, and LM/LP. Each symbol represents H for high, L for low, M for doctor, and P for pharmacist. The primary study outcome was the incidence of atherosclerotic cardiovascular disease (ASCVD). Results 126,710 patients were included. Percentages of patients in the four study groups were as follows: HM/HP 35%, HM/LP 19%, LM/HP 12%, and LM/LP 34%. During the seven-year outcome period, 8,337 patients (6.6%) developed an ASCVD, and percentages in the study groups were as follows; HM/HP 6.2%, HM/LP 6.3%, LM/HP 6.8%, and LM/LP 7.1%. After adjusting for confounding covariates, only the LM/LP group had a significantly higher risk of ASCVD than the reference group, HM/HP (aHR = 1.16 [95% confidence interval = 1.10~1.22]). The risk of inappropriate medication adherence gradually increased 1.03-fold in the HM/LP group, 1.67-fold in the LM/HP, and 2.26-fold in the LM/LP group versus the HM/HP group after adjusting for covariates. Disease-related costs were lower in the HM/HP and LM/HP groups. Conclusions The study shows that patients with high relational care continuity with doctors and pharmacists achieved better clinical results and utilized health care less, resulting in reduced expenses. Further exploration for the group that exhibits an ongoing relationship solely with pharmacists is warranted.

Objective:Systemic lupus erythematosus (SLE) is characterised by variability of disease activity patterns over time. This study aimed to investigate the trajectories of SLE disease severity patterns, identify clinical and demographic variables, and assess the association between trajectories of SLE disease severity and all-cause mortality. Methods:A retrospective cohort of newly diagnosed patients with SLE was established using the Korean nationwide healthcare claims information database between 1st January 2008 and 31st December 2016. Using group-based trajectory modelling (GBTM), they were clustered based on the trajectory of SLE disease severity patterns during a two-year follow-up from the cohort entry date. We performed Cox proportional hazards models to compare the mortality between trajectories of SLE disease severity patterns. Results:A total of 8901 patients with SLE were included in the analysis from 2008 to 2016. Five distinct SLE disease severity trajectories were identified as optimal: consistently severe (4.6 %), mild-then-moderate (11.6 %), moderate-then-mild (15.1 %), consistently moderate (30.4 %), and consistently mild (38.3 %). Patients with consistently mild disease severity were more likely to be older; those with consistently severe disease severity were more likely to be male with more comorbidities than other groups. Compared to the consistently mild disease severity, the other trajectory groups showed a higher risk of all-cause mortality. Conclusion:Through GBTM, dynamic two-year severity trajectories of newly diagnosed SLE were identified. Patients' demographics and comorbidities attributed to changes in SLE severity trajectories, which may inform evidence for clinical decision-making.

Existing evidence regarding the impact of continuity of care (COC) in asthma patients is limited, and its quality is low to moderate. This study aimed to investigate associations between relational COC within primary care and asthma-related hospitalizations in children using a robust methodology. This study is a population-based cohort study that utilized a national claims database in South Korea. The study comprised 136,296 individuals under 20 years old who were newly diagnosed with asthma between 2015 and 2016. These were classified into high, medium, and low continuity groups based on the continuity of care index (COCI). The primary outcome measure was the incidence of asthma-related hospitalizations. During a two-year follow-up period, 10,922 patients (8.01%) were hospitalized: 2520 (5.59%) in the high-continuity group, 3188 (6.98%) in the medium-continuity group, and 3867 (8.48%) in the low-continuity group. After adjusting for confounding covariates, patients in the low- and medium-continuity groups exhibited significantly higher risks of hospital admission (adjusted hazard ratio (aHR) = 1.30 [95% confidence interval = 1.24-1.37] and aHR = 1.14 [1.08-1.20], than those in the high-continuity group. Sensitivity and subgroup analyses findings were consistent. In a young population with asthma increased continuity of primary care was associated with less hospitalization.

To determine the increased risk of major adverse cardiovascular events (MACE) in patients with systemic lupus erythematosus (SLE) compared to the general population in Korea. Using data from the National Health Insurance Service database spanning 2008 to 2018, incident SLE patients aged 18 years and above were selected along with a 1:4 age- and sex-matched control group. The crude incidence rate (IR) of MACE was calculated as the number of events per 1000 person-years and the IR ratio (IRR) for MACE was adjusted using generalized estimating equations. Subgroup analysis was conducted to evaluate the risk differences of overall MACE and its composites based on age and sex stratification. The study included 8568 SLE patients and 34,272 controls. The cumulative IR of MACE per 1000 person-years in SLE patients and controls were 4.08 and 1.30, respectively. After adjusting for confounders, SLE patients had a higher risk of MACE compared to the general population (adjusted IRR of 2.40 [95% confidence interval [CI] 1.88–3.05]), with no gender differences observed. The increased risk of MACE in SLE patients was highest in the 18–39 age group (IRR 11.70, 95% CI 5.95–23.01) and gradually decreased with age. The increased risk of ischemic stroke (IRR 2.41, 95% CI 1.84–3.15) and myocardial infarction (IRR 2.19, 95% CI 1.30–3.68) in SLE patients was comparable. The risk of MACE in SLE patients is 2.40 times higher than that of the general population, with a higher relative risk observed in younger individuals.

Objectives The existing evidence for the impacts of continuity of care (COC) in patients with chronic obstructive pulmonary disease (COPD) is low to moderate. This study aimed to investigate the associations between relational COC within primary care and COPD-related hospitalisations using a robust methodology.Design Population-based cohort study.Setting National Health Insurance Service database, South Korea.Participants 92 977 adults (≥40 years) with COPD newly diagnosed between 2015 and 2016 were included. The propensity score (PS) matching approach was used. PSs were calculated from a multivariable logistic regression that included eight baseline characteristics.Exposure COC within primary care.Main outcome measures The primary outcome was the incidence of COPD-related hospitalisations. Cox proportional hazard models were used to estimate HRs and 95% CIs.Results Out of 92 977 patients, 66 677 of whom were cared for continuously by primary doctors (the continuity group), while 26 300 were not (the non-continuity group). During a 4-year follow-up period, 2094 patients (2.25%) were hospitalised; 874 (1.31%) from the continuity group and 1220 (4.64%) from the non-continuity group. After adjusting for confounding covariates, patients in the non-continuity group exhibited a significantly higher risk of hospital admission (adjusted HR (aHR) 2.43 (95% CI 2.22 to 2.66)). This risk was marginally reduced to 2.21 (95% CI 1.99 to 2.46) after PS matching. The risk of emergency department (ED) visits, systemic corticosteroid use and costs were higher for patients in the non-continuity group (aHR 2.32 (95% CI 2.04 to 2.63), adjusted OR 1.25 (95% CI 1.19 to 1.31) and expβ=1.89 (95% CI 1.82 to 1.97), respectively). These findings remained consistent across the PS-matched cohort, as well as in the sensitivity and subgroup analyses.Conclusions In patients with COPD aged over 40, increased continuity of primary care was found to be associated with less hospitalisation, fewer ED visits and lower healthcare expenditure.

Objectives To estimate the direct healthcare cost progression from before to after systemic lupus erythematosus (SLE) diagnosis and to compare healthcare costs by disease severity.Methods Patients with incident SLE diagnosed between 2008 and 2018 were identified from the Korean National Health Insurance database. Annual direct healthcare costs for 5 years before and after SLE were estimated and compared with those of age-, sex- and calendar month-matched (1:4) controls, without SLE. Direct healthcare costs were compared by disease severity of SLE using regression analysis.Results Among 11 173 patients with SLE and 45 500 subjects without SLE, annual direct healthcare costs per person increased in the year before SLE diagnosis and peaked in the first year after diagnosis. They were 7.7-fold greater in the SLE patients than in the subjects without SLE ($5871 vs $759). Severe SLE was associated with 3.284-fold (95% CI: 3.075, 3.507) higher annual costs than mild SLE during the year after diagnosis. Older age (age 60-79 years), lupus nephritis, interstitial lung diseases, and comorbidities such as avascular necrosis and chronic kidney disease were associated with higher annual direct healthcare costs (times [95% CI]) in the first year after diagnosis: age 60-69: 1.119 (1.034, 1.211); age 70-79: 1.470 (1.342, 1.611); lupus nephritis: 1.794 (1.711, 1.881); interstitial lung diseases: 1.435 (1.258, 1.638); avascular necrosis: 6.208 (4.541, 8.487); and chronic kidney disease: 1.858 (1.673, 2.064).Conclusion Patients with SLE incurred significantly higher direct healthcare costs than subjects without SLE during the first year after diagnosis. Disease severity, older age, major organ involvements and comorbidities were associated with increased healthcare costs.