Korean National Health Insurance Service Research Articles

A potential association between COVID-19 vaccination and development of alzheimer's disease.

The challenges of the COVID-19 pandemic extend to concerns about vaccine side effects, particularly potential links to neurodegenerative diseases such as Alzheimer's disease (AD). This study investigates the association between COVID-19 vaccination and the onset of AD and its prodromal state, mild cognitive impairment (MCI). A nationwide, retrospective cohort study leveraging data from the Korean National Health Insurance Service was conducted. The study, conducted in Seoul, South Korea, analyzed data from a random 50% sample of city residents aged 65 and above, totaling 558,017 individuals. Participants were divided into vaccinated and unvaccinated groups, with vaccinations including mRNA and cDNA vaccines. The study focused on AD and MCI incidences post-vaccination, identified via ICD-10 codes, using multivariable logistic and Cox regression analyses. Patients with vascular dementia or Parkinson's disease served as controls. Findings showed an increased incidence of MCI and AD in vaccinated individuals, particularly those receiving mRNA vaccines, within three months post-vaccination. The mRNA vaccine group exhibited a significantly higher incidence of AD (Odds Ratio [OR]: 1.225; 95% Confidence Interval [CI]: 1.025-1.464; p = 0.026) and MCI (OR: 2.377; CI: 1.845-3.064; p < 0.001) compared to the unvaccinated group. No significant relationship was found with vascular dementia or Parkinson's disease. Preliminary evidence suggests a potential link between COVID-19 vaccination, particularly mRNA vaccines, and increased incidences of AD and MCI. This underscores the need for further research to elucidate the relationship between vaccine-induced immune responses and neurodegenerative processes, advocating for continuous monitoring and investigation into the vaccines' long-term neurological impacts.

Physical activity change after early rhythm control after new-onset atrial fibrillation and major adverse cardiovascular event risk

Abstract Background There is paucity of information about major adverse cardiovascular event (MACE) related to physical activity change after early rhythm control (ERC) after new-onset atrial fibrillation (AF). We investigated the association between physical activity after ERC and clinical outcomes in new-onset AF patients. Methods This study was performed based on the Korean National Health Insurance Service database. We included adults with new-onset AF between 2009 and 2018. Patients who received national health screening examination before and after AF diagnosis within 2-year were finally included (n=161,379). Among these, 48,243 patients were received rhythm control within 2-year after AF diagnosis. Patients were categorized into 4 groups as follows: persistent non-exerciser, new exerciser (after AF diagnosis and ERC), exercise maintainer, and exercise quitter (after AF diagnosis and ERC). The primary outcome was MACE defined as the composite of ischemic stroke, myocardial infarction, and hospitalization for heart failure. Multivariable Cox analysis was performed. Results Among 48,243 patients receiving ERC, 63% (n=30,540) was persistent non-exerciser, 13% (n=6260) was new exerciser, 11% (n=5102) was exercise maintainer, and 13% (n=6341) was exercise quitter. After multivariable adjustment, compared to persistent non-exerciser, new exerciser and exercise maintainer with ERC showed lower risk of MACE by 10% and 19%, respectively (adjusted hazard ratio [aHR], 95% confidence interval [95% CI], 0.903 [0.802-0.994] for new exerciser, and 0.810 [0.725-0.906] for exercise maintainer) (Table 1). However, exercise quitter did not show significant benefit compared to persistent non-exerciser (Table 1). To assess the synergistic effect of ERC and starting or maintaining physical activity, we performed exploratory analysis including patients who did not receive ERC. Compared to persistent non-exerciser without ERC, persistent non-exerciser with ERC was associated with a significantly lower risk of MACE (0.832 [0.797-0.868], Table 2). Patients who received ERC and started or maintained physical activity with ERC showed greatest risk reduction for MACE by 27% and 36%, respectively (0.732 [0.668-0.802] for new exerciser and 0.641 [0.576-0.713] for exercise maintainer) (Table 2). Conclusion Even in context with beneficial effect of ERC in patients with new-onset AF, maintaining or starting regular physical activity after ERC might bring greater reduction on the risk of MACE. Physician should emphasize healthy lifestyle behavior with rhythm control in patients with new-onset AF.

Obesity paradox in atrial fibrillation patients on oral anticoagulation therapy: a Korean nationwide cohort study

Abstract Background The obesity paradox is a phenomenon that has been observed in specific pathological conditions, wherein individuals who are overweight or obese exhibit a survival advantage over those with a normal weight. This phenomenon has also been noted in patients diagnosed with atrial fibrillation (AF), although the impact of body mass index (BMI) on clinical outcomes in AF patients undergoing oral anticoagulant (OAC) therapy remains uncertain. Purpose The aim of this study was to investigate the potential relationship between obesity and cardiovascular outcomes in patients diagnosed with AF who were receiving OAC. Methods We utilized administrative claims data from the Korean National Health Insurance Service and the combined health check-up database of the National Health Insurance Corporation to conduct a retrospective national cohort study spanning from 2013 to 2020. The patients newly prescribed OAC for AF were included, between January 2015 and December 2019. We followed up with patients from their index date until each outcome event or the end of the study period. BMI was categorized into 5 groups based on the World Health Organization's recommended criteria for Asian populations. The predefined clinical outcomes included thromboembolism, major bleeding, all-cause death, and the composite outcome. Results A total of 35,333 patients were included in the study. The mean age was 69 ± 10 years, and 37.1% were female. During a median follow-up of 2.0 years (IQR, 0.4–3.3), there were 11,634 thromboembolic events, 1,521 major bleeding events, and 2,586 deaths. The adjusted hazard ratio (HR) for thromboembolism, major bleeding, all-cause death, and a composite outcome were lower in obese II group (HR 0.79, 95% CI 0.73–0.86; HR 0.99, 95% CI 0.79–1.24; HR 0.75, 95% CI 0.62–0.91; HR 0.81, 95% CI 0.75–0.88) compared to the normal range BMI group. Conclusions In AF patients undergoing OAC therapy, individuals classified as obese exhibited a reduced risk of thromboembolism, major bleeding, all-cause mortality, and composite outcome compared to patients with normal weight.Adjusted hazard ratio of outcomes by BMI

Pregnancy related complications in women with hypertrophic cardiomyopathy: a nationwide population-based cohort study

BackgroundThe impact of hypertrophic cardiomyopathy (HCM) on cardiovascular and obstetrical outcomes in pregnant women remains unclear, particularly in Asian populations. This study aimed to evaluate the maternal cardiovascular and obstetrical outcomes in Korean women with HCM.MethodsUsing data from the Korean National Health Insurance Service database, we identified women who gave birth via cesarean section or vaginal delivery after being diagnosed with HCM between 2006 and 2019. Maternal cardiovascular and obstetrical outcomes were assessed based on the trimester of pregnancy.ResultsThis study included 122 women and 158 pregnancies. No maternal deaths were noted; however, 21 cardiovascular events, such as hospital admission for cardiac problems, including heart failure and atrial fibrillation (AF), new-onset AF or ventricular tachycardia (VT) occurred in 14 pregnancies (8.8%). Cardiac events occurred throughout pregnancy with a higher occurrence in the third trimester. Cesarean sections were performed in 49.3% of the cases, and all cardiovascular outcomes occurring after delivery were observed in patients who had undergone cesarean sections. Seven cases involved preterm delivery, and two of these cases were accompanied by cardiac events, specifically AF. Pre-existing arrhythmia (AF: odds ratio (OR): 7.44, 95% confidence interval (CI): 2.61–21.21, P < 0.001; VT: OR: 31.61, 95% CI: 5.85–172.77, P < 0.001) was identified as a predictor for composite outcomes of cardiovascular events or preterm delivery.ConclusionsMost pregnant women with HCM were well-tolerated. However, cardiovascular complications could occur in some patients. Therefore, planned delivery may be necessary for selected patients, especially the women with pre-existing arrhythmias.

Cumulative effect of metabolic syndrome on the risk of retinal vein occlusion in young patients: A nationwide population-based study.

This study aimed to investigate the impact of the cumulative burden of metabolic syndrome (MetS) on the incidence of retinal vein occlusion (RVO) in young adults. We included 1,408,093 subjects aged ≥20 and <40 years without a history of RVO who underwent four consecutive annual health examinations during 2009-2012 from the database of the Korean National Health Insurance Service. The metabolic burden was evaluated based on the cumulative number of MetS diagnoses at each health examination (0-4 times) and the cumulative number of each MetS component diagnosed at each health examination (0-4 times per MetS component). Cox proportional hazards models were used to estimate the risk of RVO according to metabolic burden. The risk of RVO was positively correlated with the cumulative number of MetS diagnoses over the four health examinations. All five MetS components were independently associated with an increased risk of RVO. Subgroup analysis for the impact of MetS on RVO occurrence revealed that MetS had a greater impact on female subjects (P <0.001). Prompt detection of metabolic derangements and their treatment might be important to decrease the risk of RVO in young adults, especially women.

Risk Factors and Mortality Among Women With Interval Breast Cancer vs Screen-Detected Breast Cancer

The risk factors for interval breast cancer (IBC) compared with those for screen-detected breast cancer (SBC) and their association with mortality outcomes have not yet been evaluated among Korean women. To evaluate risk factors associated with IBC and survival among Korean women with IBC compared with those with SBC. This retrospective cohort study used data from the Korean National Health Insurance Service Database. Women who participated in a national mammographic breast cancer screening program between January 1, 2009, and December 31, 2012, were included. Mortality outcomes were calculated from the date of breast cancer diagnosis to the date of death or December 31, 2020. Data were analyzed from March 1 to June 30, 2023. Breast cancer diagnosed within 6 to 24 months after a negative screening result (ie, IBC) or within 6 months after a positive screening result (ie, SBC). Risk factors and survival rates for IBC and SBC. This study included 8702 women with IBC (mean [SD] age, 53.3 [8.6] years) and 9492 women with SBC (mean [SD] age, 54.1 [9.0] years). Compared with SBC, the probability of IBC decreased as mammographic density increased. Lower body mass index, menopausal status, hormone replacement therapy (HRT) use, and lack of family history of breast cancer were associated with a higher likelihood of IBC. When stratified by detection time, younger age at breast cancer diagnosis and family history of breast cancer were associated with an increased likelihood of IBC diagnosed at 6 to 12 months but a decreased likelihood of IBC diagnosed at 12 to 24 months. Overall mortality of IBC was comparable with SBC, but total mortality and cancer-related mortality of IBC diagnosed between 6 and 12 months was higher than that of SBC. The findings of this cohort study suggest that breast density, obesity, and HRT use were associated with IBC compared with SBC. These findings also suggest that higher supplemental breast ultrasound use among Korean women, especially those with dense breasts, could be attributed to a lower incidence of IBC among women with dense breasts compared with women with SBC, due to greater detection. Finally, overall mortality of IBC was comparable with that of SBC.

Risk of Head and Neck Cancer in Patients with Psoriasis: A Nationwide Population-based Study.

An association between psoriasis and cancer risk has been suggested in prior studies, but few have focused on head and neck cancers. Using the Korean National Health Insurance Service database, the relevance between psoriasis and head and neck cancer risks was investigated in a cross-sectional study of 3,869,264 individuals over 20 years of age, who received general health examination in 2009 and were followed until 2020. Head and neck cancer incidence rates were compared between individuals with and without psoriasis, and contributing factors were analysed. The head and neck cancer risk was significantly increased in the psoriasis group compared with the non-psoriasis group (hazard ratio [HR] 1.36; 95% confidence interval [CI] 1.07-1.74; p = 0.01) after adjusting for age, sex, body mass index, income, smoking, alcohol, exercise, diabetes mellitus, hypertension and dyslipidaemia. The risk was especially elevated for nasopharyngeal (HR 2.04; 95% CI 1.12-3.70; p = 0.02) and salivary gland cancer (HR 1.96; 95% CI 1.08-3.56; p = 0.03). Alcohol consumption significantly influenced the risk, particularly for oropharyngeal and oral cavity cancer. Our study provides insights into the potential risks of head and neck cancer in patients with psoriasis, which could aid in refining patient management strategies.

Risk factors for middle ear cholesteatoma surgery based on Korean population data

Background Studies of risk factors for middle ear cholesteatoma surgery using population-based data are lacking. Objectives To investigate the risk factors for cholesteatoma surgery in adults based on population data from Korea. Materials and Methods For this retrospective study, we used Korean National Health Insurance Service National Sample Cohort data. Patients who were 20 years or older and underwent mastoidectomy from 2006 through 2015 under the diagnostic codes of cholesteatoma were defined as patients with middle ear cholesteatoma surgery. The control group was comprised of the remaining database sample in 2006. Sociodemographic factors in 2006 and histories of medical diseases, allergic diseases, and chronic sinusitis from 2003 through 2005 were compared between cholesteatoma surgery and control groups. Results A total of 459 patients underwent cholesteatoma surgery. In multivariate Cox regression analysis, age 40–59 years and residence in metropolitan cities and small- and medium-sized cities and counties were significant risk factors for cholesteatoma surgery whereas allergic rhinitis, asthma, atopic dermatitis, and chronic sinusitis were not significant risk factors for middle ear cholesteatoma surgery. Conclusions and significance The present study found no evidence of associations between allergic diseases or chronic sinusitis and cholesteatoma surgery in adults.

Sex differences in prognosis factors in patients with lung cancer: A nationwide retrospective cohort study in Korea.

Large-scale studies elucidating sex differences in factors impacting prognosis and sex-specific prognossis factors scoring in patients with lung cancer are insufficient. The present study aimed to develop a model to predict sex-specific prognosis factors in Korean patients with lung cancer. This nationwide cohort study included 96,255 patients aged ≥19 years diagnosed with lung cancer and underwent Korean National Health Insurance Service health examinations between January 1, 2005 and December 31, 2015 and followed until 2020. Factors associated with prognosis were estimated using multivariable Cox proportional hazards regression analyses, and separate prognosis scores were calculated for male and female patients. The sex-specific risk scoring models were validated with Kaplan-Meier survival curves and c-statistic. During a mean follow-up of 2.8 years, 60.5% of the patients died. In male patients with lung cancer, age ≥ 65 years (24 points) had the highest mortality risk score, followed by chemotherapy in combination with radiotherapy (16 points), chemotherapy (14 points), and radiotherapy (11 points). In female patients with lung cancer, chemotherapy in combination with radiotherapy (19 points) had the highest mortality risk score, followed by chemotherapy (16 points), age ≥ 65 years (13 points), and radiotherapy (13 points). The analysis of patients categorized into three risk groups based on risk scores revealed that the fatality rates within 5 years were 7%, 54%, and 89% in the low-, intermediate-, and high-risk groups for male patients and 3%, 46%, 85% in the low-, intermediate-, and high-risk groups for female patients, respectively. The c-statistic was 0.86 for male patients and 0.85 for female patients. The strongest fatality risk factors in lung cancer were age ≥ 65 years in male patients and chemotherapy in female patients. The present study developed sex-specific prognosis scoring models to predict fatality risk in patients with lung cancer.

SARS-CoV-2 vaccine effectiveness and clinical outcomes in hemodialysis patients: the NHIS-COVID-19 cohort study in South Korea.

Patients undergoing hemodialysis (HD) have a high risk of novel coronavirus disease 2019 (COVID-19) and poor clinical outcomes. This study aimed to investigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine effectiveness against infection and deaths in the South Korean population undergoing HD. We conducted a retrospective cohort study to compare the incidence of COVID-19 and post-diagnosis mortality between patients who were either never vaccinated or fully or partially vaccinated. The Korean nationwide COVID-19 registry and the Korean National Health Insurance Service databases were used. Adult patients without a history of COVID-19 were included between October 8, 2020, and December 31, 2021. The study outcomes were COVID-19 diagnosis, severe clinical COVID-19-related events, and post-diagnosis death. Eighty-five thousand eighteen patients undergoing HD were included, of whom 69,601 were fully vaccinated, 2,213 were partially vaccinated and 13,204 were unvaccinated. Compared with the unvaccinated group, the risk of being diagnosed with COVID-19 in patients who were fully vaccinated decreased during the study period (adjusted odds ratio [aOR] = 0.147; 95% confidence interval [CI] = 0.135-0.159). There were 1,140 (1.3%) patients diagnosed with COVID-19. After diagnosis, fully vaccinated patients were significantly less likely to die than unvaccinated patients (aOR = 0.940; 95% CI = 0.901-0.980) and to experience severe clinical events (aOR = 0.952; 95% CI = 0.916-0.988). Full vaccination against COVID-19 was associated with a reduced risk of both infection and severe clinical outcomes in the South Korean population undergoing HD. These findings support the use of vaccination against SARS-CoV-2 among patients undergoing HD.

Association between physical activity changes and risk of incident ischemic stroke following cancer diagnosis: A nationwide retrospective cohort study.

Physical inactivity is prevalent after cancer treatment, which could increase ischemic stroke risk in cancer survivors. This study investigated the association between physical activity change from pre- to post-diagnosis and ischemic stroke risk among cancer survivors. Using data from the Korean National Health Insurance Service database, 269,943 cancer survivors (mean [SD] age, 56.3 [12.1] years; 45.7% male) with no history of cardiovascular disease were evaluated based on changes in physical activity from pre- to post-diagnosis. Using the Fine-Gray model, subdistribution hazard ratios (sHRs) and 95% confidence intervals (CIs) for ischemic stroke risk were calculated, considering death as a competing risk. After cancer diagnosis, 62.0% remained inactive, 10.1% remained active, 16.6% became active, and 11.4% became inactive. During a mean (SD) follow-up of 4.1 (2.0) years, being active both pre- and post-diagnosis was associated with a 15% decreased risk of ischemic stroke (sHR, 0.85; 95% CI, 0.75-0.96), compared with those who remained inactive. Cancer survivors who became active and inactive post-diagnosis showed a 16% and 11% lower ischemic stroke risk (sHR, 0.84; 95% CI, 0.75-0.93; sHR, 0.89; 95% CI, 0.79-0.99), respectively, than those who remained inactive. Analysis by the primary cancer site did not substantially differ from the main findings. Physical activity is associated with reduced ischemic stroke risk among cancer survivors. The potential benefits of physical activity are not limited to individuals who were physically active before cancer diagnosis, thus preventive strategies against ischemic stroke should emphasize physical activity throughout the cancer journey.

Association between physical activity changes and incident myocardial infarction after ischemic stroke: a nationwide population-based study

BackgroundThe impact of changes in physical activity after ischemic stroke (IS) on the subsequent myocardial infarction (MI) risk is not fully understood. We aimed to investigate the effects of changes in physical activity on the risk of MI after acute IS using data from the Korean National Health Insurance Services Database.Methods224,764 patients newly diagnosed with IS between 2010 and 2016 who underwent two serial biannual health checkups were included. The participants were divided into four categories according to changes in their physical activity: persistent non-exercisers, new exercisers, exercise dropouts, and exercise maintainers. The primary outcome was a new diagnosis of incident MI. Multivariable Cox proportional models were used to assess the effects of changes in exercise habits on the risk of MI.ResultsAfter a median of 4.25 years of follow-up, 6,611 (2.94%) MI cases were observed. After adjusting for confounders, new exercisers and exercise maintainers were significantly associated with a lower risk of incident MI than persistent non-exercisers (aHR, 0.849; 95% CI, 0.792–0.911; P-value < 0.001; and aHR, 0.746; 95% CI, 0.696–0.801; P-value < 0.001, respectively). Effects were consistent across sexes, more pronounced in those > 65 years. Notably, any level of physical activity after stroke was associated with a reduced MI risk compared to no exercise.ConclusionsIn this nationwide cohort study, commencing or sustaining physical activity after an IS corresponded to a diminished likelihood of subsequent MI development. Advocating physical activity in ambulatory stroke survivors could potentially attenuate the prospective risk of MI.

Differences in end-of-life care patterns between types of hospice used for cancer patients: a retrospective cohort study.

In response to the rapid aging population and increasing number of cancer patients, discussions on dignified end-of-life (EoL) decisions are active around the world. Therefore, this study aimed to identify the differences in EoL care patterns between types of hospice used for cancer patients. In this population-based cohort study, the Korean National Health Insurance Service cohort data containing all registered cancer patients who died between 2017 and 2021 were used. A total of 408,964 individuals were eligible for analysis. The variable of interest, the type of hospice used in the 6months before death, was classified as follows: (1) Non-hospice users; (2) Hospital-based hospice single users; (3) Home-based hospice single users; (4) Combined hospice users. The outcomes were set as patterns of care, including intense care and supportive care. To identify differences in care patterns between hospice types, a generalized linear model with zero-inflated negative binomial distribution was applied. Hospice enrollment was associated with less intense care and more supportive care near death. Notably, those who used combined hospice care had the lowest probability and frequency of receiving intense care (aOR: 0.18, 95% CI: 0.17-0.19, aRR: 0.47, 95% CI: 0.44-0.49), while home-based hospice single users had the highest probability and frequency of receiving supportive care (Prescription for narcotic analgesics, aOR: 2.95, 95% CI: 2.69-3.23, aRR: 1.45, 95% CI: 1.41-1.49; Mental health care, aOR: 3.40, 95% CI: 3.13-3.69, aRR: 1.35, 95% CI: 1.31-1.39). Our findings suggest that although intense care for life-sustaining decreases with hospice enrollment, QoL at the EoL actually improves with appropriate supportive care. This study is meaningful in that it not only offers valuable insight into hospice care for terminally ill patients, but also provides policy implications for the introduction of patient-centered community-based hospice services.

Outcomes of non-vitamin K oral anticoagulants for secondary prevention in ischemic stroke with atrial fibrillation

Previous studies have rarely investigated the role of non-vitamin K oral anticoagulants (NOAC) and warfarin in the secondary prevention of ischemic stroke patients with nonvalvular atrial fibrillation (NVAF). In this study, we compared the effectiveness and safety of NOAC and warfarin for secondary prevention in Korean ischemic stroke patients with NVAF. Based on the Korean National Health Insurance Service Database, this study included 21,064 oral anticoagulants-naïve acute ischemic stroke patients with NVAF between July 2015 and June 2019. The main study outcomes included ischemic stroke, systemic embolism, major bleeding, and death. During the observational periods, NOAC users had a significantly decreased risk of ischemic stroke + systemic embolism (adjusted hazard ratio [aHR] 0.86; 95% confidence interval [CI] 0.78–0.95), ischemic stroke (aHR 0.89; 95% CI 0.81–0.99), major bleeding (aHR 0.78; 95% CI 0.68–0.89), and all-cause death (aHR 0.87; 95% CI 0.81–0.93). Standard-dose NOAC users had a lower risk of ischemic stroke, systemic embolism, and major bleeding events than warfarin users. In contrast, low-dose NOAC users did not differ in risk from warfarin users for all outcomes. In conclusion, NOACs were associated with a lower risk of secondary thromboembolic events and bleeding complications in Korean ischemic stroke patients with NVAF than warfarin.

The influence of advanced maternal age on congenital malformations, short- and long-term outcomes in offspring of nulligravida: a Korean National Cohort Study over 15 years.

To assess the influence of advanced maternal age on congenital malformations, and short- and long-term outcomes in offspring of nulligravida. A retrospective study was conducted using the Korean National Health Insurance Service database spanning from January 2005 to December 2019. All live-born offspring of nulligravida (n=3,685,817) were included. The maternal age was subdivided into the following subgroups: <25 years (n=153,818), 25-29 years (n=845,355), 30-34 years (n=1,738,299), 35-39 years (n=787,530), 40-44 years (n=151,519), and >44 years (n=9,296). Outcomes were assessed based on ICD-10 codes. Adjusted odds ratios (aORs) were calculated with the group of 25-29 years as a reference using logistic regression and Cox proportional hazards model analysis. Most congenital malformations showed an age-dependent increase, but cleft lip and abdominal wall defect exhibited a U-shape curve, indicating an increase even in those <25 years old. Similarly, various disorders included in the neonatal composite outcomes from short-term outcomes showed an age-dependent escalation. However, preterm birth from the short-term outcomes and most of the long-term developmental outcomes, except for motor developmental delays and Tics, showed a U-shaped pattern. The aOR of autism and cerebral palsy, showing the most obvious U-shaped curved in the long-term outcomes, was 1.50 (95% CI 1.24-1.82) and 1.54 (95% CI 1.17-2.03), respectively in the >44 years old group and 1.18 (95% confidence interval [CI], 1.11-1.25) and 1.19 (95% CI, 1.09-1.30) in the <25 years old group. Overall, an advanced maternal age shows an age-dependent correlation with most congenital malformations, as well as short- and long-term outcomes of neonates.

Income variability and incident cardiovascular disease in diabetes: a population-based cohort study.

Longitudinal change in income is crucial in explaining cardiovascular health inequalities. However, there is limited evidence for cardiovascular disease (CVD) risk associated with income dynamics over time among individuals with type 2 diabetes (T2D). Using a nationally representative sample from the Korean National Health Insurance Service database, 1 528 108 adults aged 30-64 with T2D and no history of CVD were included from 2009 to 2012 (mean follow-up of 7.3 years). Using monthly health insurance premium information, income levels were assessed annually for the baseline year and the four preceding years. Income variability was defined as the intraindividual standard deviation of the percent change in income over 5 years. The primary outcome was a composite event of incident fatal and nonfatal CVD (myocardial infarction, heart failure, and stroke) using insurance claims. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated after adjusting for potential confounders. High-income variability was associated with increased CVD risk (HRhighest vs. lowest quartile 1.25, 95% CI 1.22-1.27; Ptrend < .001). Individuals who experienced an income decline (4 years ago vs. baseline) had increased CVD risk, which was particularly notable when the income decreased to the lowest level (i.e. Medical Aid beneficiaries), regardless of their initial income status. Sustained low income (i.e. lowest income quartile) over 5 years was associated with increased CVD risk (HRn = 5 years vs. n = 0 years 1.38, 95% CI 1.35-1.41; Ptrend < .0001), whereas sustained high income (i.e. highest income quartile) was associated with decreased CVD risk (HRn = 5 years vs. n = 0 years 0.71, 95% CI 0.70-0.72; Ptrend < .0001). Sensitivity analyses, exploring potential mediators, such as lifestyle-related factors and obesity, supported the main results. Higher income variability, income declines, and sustained low income were associated with increased CVD risk. Our findings highlight the need to better understand the mechanisms by which income dynamics impact CVD risk among individuals with T2D.

Musculoskeletal morbidity in adults with spinal cord injuries: A nationwide cohort study.

An increase in the demand for quality of life following spinal cord injuries (SCIs) is associated with an increase in musculoskeletal (MSK) pain, highlighting the need for preventive measure research. This study aimed to evaluate the incidence and hazards of MSK morbidities among Korean adults with SCIs, as well as the influence of SCI location on MSK morbidities. Patient populations were selected from Korean National Health Insurance Service data (n = 276). The control group included individuals without SCIs (n = 10,000). We compared the incidences and determined the unadjusted and adjusted hazard ratios (HRs) of common MSK morbidities (osteoarthritis, connective tissue disorders, sarcopenia, myalgia, neuralgia, rheumatoid arthritis, myositis, and musculoskeletal infections) based on the location of injury (cervical, thoracic, or lumbar). Adults with SCIs had a higher incidence of MSK morbidity (48.45% vs. 36.6%) and a lower survival probability than those without SCIs. The incidence of MSK morbidity and survival probabilities were not significantly different for cervical cord injuries, whereas both measures were significantly different for thoracic and lumbar injuries. SCI increases the risk of MSK morbidity. Lumbar SCI is associated with a higher incidence and risk of MSK morbidity than are cervical or thoracic SCIs.

Effects of risk factors on the development and mortality of early- and late-onset dementia: an 11-year longitudinal nationwide population-based cohort study in South Korea

BackgroundEarly-onset dementia (EOD, onset age < 65) and late-onset dementia (LOD, onset age ≥ 65) exhibit distinct features. Understanding the risk factors for dementia development and mortality in EOD and LOD respectively is crucial for personalized care. While risk factors are known for LOD development and mortality, their impact on EOD remains unclear. We aimed to investigate how hypertension, diabetes mellitus, hyperlipidemia, atrial fibrillation, and osteoporosis influence the development and mortality of EOD and LOD, respectively.MethodsUsing the Korean National Health Insurance Service (NHIS) database, we collected 546,709 dementia-free individuals and followed up for 11 years. In the two study groups, the Younger group (< 65 years old) and the Older group (≥ 65 years old), we applied Cox proportional hazard models to assess risk factors for development of EOD and LOD, respectively. Then, we assessed risk factors for mortality among EOD and LOD.ResultsDiabetes mellitus and osteoporosis increased the risk of EOD and LOD development. Hypertension increased the risk of EOD, while atrial fibrillation increased the risk of LOD. Conversely, hyperlipidemia exhibited a protective effect against LOD development. Additionally, diabetes mellitus increased mortality in EOD and LOD. Hypertension and atrial fibrillation increased mortality in LOD, while hyperlipidemia decreased mortality in EOD and LOD.ConclusionsRisk factors influencing dementia development and mortality differed in EOD and LOD. Targeted public health interventions addressing age-related risk factors may reduce dementia incidence and mortality.

COVID-19 Vaccine–Associated Uveitis in Patients With a History of Uveitis

Understanding the potential risk of uveitis recurrence after COVID-19 vaccination in individuals with a history of uveitis is crucial for vaccination strategies and clinical monitoring. To investigate the risk of uveitis recurrence after COVID-19 vaccination in a cohort of individuals with a history of uveitis. This retrospective population-based cohort study included individuals diagnosed with uveitis between January 1, 2015, and February 25, 2021, in South Korea. After excluding individuals without COVID-19 vaccination or with SARS-CoV-2 infection, individuals with a history of uveitis who had received at least 1 dose of a messenger RNA (BNT162b2 [Pfizer-BioNTech] or mRNA-1273 [Moderna]) or adenovirus vector-based (ChAdOx1 [AstraZeneca] or Ad26.COV2.S [Janssen]) COVID-19 vaccine were included. Data were analyzed from February 26, 2021, to December 31, 2022. Demographic and clinical data, along with vaccination details, were retrieved from the Korean National Health Insurance Service and Korea Disease Control and Prevention Agency databases. Outcomes of interest were incidence and risk of postvaccination uveitis in association with different COVID-19 vaccines and periods before and after COVID-19 vaccination. Uveitis was categorized by onset (early, within 30 days, or delayed) and type (anterior or nonanterior). Hazard ratios (HRs) with 95% CIs were calculated to evaluate the risk of uveitis following COVID-19 vaccination, stratified according to vaccine type and vaccination period. Of 543 737 individuals with history of uveitis, 473 934 individuals (mean [SD] age, 58.9 [17.4] years; 243 127 [51.3] female) had documented COVID-19 vaccination and were included in analysis. The cumulative incidence of postvaccination uveitis was 8.6% at 3 months, 12.5% at 6 months, and 16.8% at 1 year, predominantly of the anterior type. Variations in the risk of postvaccination uveitis were observed across different vaccines and intervaccination periods. The risk of early postvaccination uveitis was increased for individuals receiving the BNT162b2 (HR, 1.68; 95% CI, 1.52-1.86), mRNA-1273 (HR, 1.51; 95% CI, 1.21-1.89), ChAdOx1 (HR, 1.60; 95% CI, 1.43-1.79), and Ad26.COV2.S (HR, 2.07; 95% CI, 1.40-3.07) vaccines. The risk of uveitis was higher particularly between the first and second vaccination doses (HR, 1.64; 95% CI, 1.55-1.73). These findings suggest that there was an elevated risk of uveitis following COVID-19 vaccination, with the vaccine type and period mediating this risk. For individuals with a history of uveitis, clinicians should consider the potential risk of uveitis recurrence in vaccination strategies and clinical monitoring.

The Impact of Infectious Mononucleosis History on the Risk of Developing Lymphoma and Nasopharyngeal Carcinoma: a Retrospective Large-Scale Cohort Study using National Health Insurance Data in South Korea.

This study aimed to assess the long-term risks associated with a history of infectious mononucleosis (IM), primarily caused by the Epstein-Barr virus (EBV). Specifically analyzing the potential increase in developing nasopharyngeal cancer (NPC) and lymphoma in patients with a history of IM and exploring the prevalence of other EBV-associated conditions. The Korean National Health Insurance Service (NHIS) database was utilized for a retrospective analysis, covering data from 2002 to 2021. A total of 25,582 IM patients and controls were included, with 1:1 propensity score matching. The study monitored outcomes, including lymphoma, NPC, gastric cancer, multiple sclerosis, and all-cause mortality. Patients with a history of IM demonstrated a significantly higher incidence of lymphoma (HR=5.32, 95% CI 3.208‒8.82, p<0.001) and NPC (HR=7.116, 95% CI 1.617‒31.314, p=0.009) during the follow-up period compared with the control group. Additionally, the IM group showed an increased rate of all-cause mortality (HR=2.225, 95% CI 1.858‒2.663, p<0.001). This study suggests that individuals with a history of IM have an elevated risk of developing lymphoma and NPC in South Korea, emphasizing the importance of vigilant follow-up and monitoring. The results advocate for heightened awareness and potential national monitoring policies to address the long-term health implications of EBV infection and to implement preventive measures.