As mounting evidence suggests a higher incidence of adverse consequences, such as disruption of the immune system, among patients with a history of COVID-19, we aimed to investigate post-COVID-19 conditions on a comprehensive set of allergic diseases including asthma, allergic rhinitis, atopic dermatitis, and food allergy. We used nationwide claims-based cohorts in South Korea (K-CoV-N; n = 836,164; main cohort) and Japan (JMDC; n = 2,541,021; replication cohort A) and the UK Biobank cohort (UKB; n = 325,843; replication cohort B) after 1:5 propensity score matching. Among the 836,164 individuals in the main cohort (mean age, 50.25 years [SD, 13.86]; 372,914 [44.6%] women), 147,824 were infected with SARS-CoV-2 during the follow-up period (2020−2021). The risk of developing allergic diseases, beyond the first 30 days of diagnosis of COVID-19, significantly increased (HR, 1.20; 95% CI, 1.13−1.27), notably in asthma (HR, 2.25; 95% CI, 1.80−2.83) and allergic rhinitis (HR, 1.23; 95% CI, 1.15−1.32). This risk gradually decreased over time, but it persisted throughout the follow-up period (≥6 months). In addition, the risk increased with increasing severity of COVID-19. Notably, COVID-19 vaccination of at least two doses had a protective effect against subsequent allergic diseases (HR, 0.81; 95% CI, 0.68−0.96). Similar findings were reported in the replication cohorts A and B. Although the potential for misclassification of pre-existing allergic conditions as incident diseases remains a limitation, ethnic diversity for evidence of incident allergic diseases in post-COVID-19 condition has been validated by utilizing multinational and independent population-based cohorts.

Some data suggest a higher incidence of diagnosis of autoimmune inflammatory rheumatic diseases (AIRDs) among patients with a history of COVID-19 compared with uninfected patients. However, these studies had methodological shortcomings. To investigate the effect of COVID-19 on long-term risk for incident AIRD over various follow-up periods. Binational, longitudinal, propensity-matched cohort study. Nationwide claims-based databases in South Korea (K-COV-N cohort) and Japan (JMDC cohort). 10 027 506 Korean and 12 218 680 Japanese patients aged 20 years or older, including those with COVID-19 between 1 January 2020 and 31 December 2021, matched to patients with influenza infection and to uninfected control patients. The primary outcome was onset of AIRD (per appropriate codes from the International Classification of Diseases, 10th Revision) 1, 6, and 12 months after COVID-19 or influenza infection or the respective matched index date of uninfected control patients. Between 2020 and 2021, among the 10 027 506 Korean participants (mean age, 48.4 years [SD, 13.4]; 50.1% men), 394 274 (3.9%) and 98 596 (0.98%) had a history of COVID-19 or influenza, respectively. After propensity score matching, beyond the first 30 days after infection, patients with COVID-19 were at increased risk for incident AIRD compared with uninfected patients (adjusted hazard ratio, 1.25 [95% CI, 1.18 to 1.31]) and influenza-infected control patients (adjusted hazard ratio, 1.30 [CI, 1.02 to 1.59]). The risk for incident AIRD was higher with more severe acute COVID-19. Similar patterns were observed in the Japanese cohort. Referral bias due to the pandemic; residual confounding. SARS-CoV-2 infection was associated with increased risk for incident AIRD compared with matched patients without SARS-CoV-2 infection or with influenza infection. The risk for incident AIRD was higher with greater severity of acute COVID-19. National Research Foundation of Korea.

Considering the significant burden of post-acute COVID-19 conditions among patients infected with SARS-CoV-2, we aimed to identify the risk of acute respiratory complications or post-acute respiratory sequelae. A binational population-based cohort study was conducted to analyze the risk of acute respiratory complications or post-acute respiratory sequelae after SARS-CoV-2 infection. We used a Korean nationwide claim-based cohort (K-COV-N; n = 2,312,748; main cohort) and a Japanese claim-based cohort (JMDC; n = 3,115,606; replication cohort) after multi-to-one propensity score matching. Among 2,312,748 Korean participants (mean age, 47.2 years [SD, 15.6]; 1,109,708 [48.0%] female), 17.1% (394,598/2,312,748) were infected with SARS-CoV-2. The risk of acute respiratory complications or post-acute respiratory sequelae is significantly increased in people with SARS-CoV-2 infection compared to the general population (acute respiratory complications: HR, 8.06 [95% CI, 6.92-9.38]; post-acute respiratory sequelae: 1.68 [1.62-1.75]), and the risk increased with increasing COVID-19 severity. We identified COVID-19 vaccination as an attenuating factor, showing a protective association against acute or post-acute respiratory conditions. Furthermore, while the excess post-acute risk diminished with time following SARS-CoV-2 infection, it persisted beyond 6 months post-infection. The replication cohort showed a similar pattern in the association. Our study comprehensively evaluates respiratory complications in post-COVID-19 conditions, considering attenuating factors such as vaccination status, post-infection duration, COVID-19 severity, and specific respiratory conditions.

The American Heart Association recently introduced a new framework, known as cardiovascular-kidney-metabolic (CKM) syndrome, aimed at the early prevention of cardiovascular disease. However, this syndrome has not been studied extensively outside of the United States. Thus, this study aimed to examine the long-term trends in CKM syndrome and its associated demographic features in South Korea. This nationwide, cross-sectional study analyzed data from 61,106 Korean adults aged ≥20 years using the Korea National Health and Nutrition Examination Survey from 2011 to 2021. CKM syndrome was defined using the PREVENT equations, categorizing individuals into five stages (0-4). Age-standardized prevalence rates, annual percent changes (APC), and sociodemographic disparities were analyzed using multinomial logistic regression and Joinpoint regression. Among the 61,106 participants (50.4% females [95% CI, 50.0-50.8%] and 49.6% males [95% CI, 49.2-50.0%]), stage 2 CKM syndrome was the most prevalent (43.4% [42.9-43.9]), followed by stages 1 (25.4% [25.0-25.8]), 0 (21.1% [20.7-21.6]), 3 (7.3% [7.0-7.5]), and 4 (2.8% [2.6-2.9]). From 2011 to 2021, advanced stages showed significant increases (APC for stage 4: 3.2%; 95% CI, 1.5-5.2), while stage 0 declined (APC: -1.9%; 95% CI, -3.8 to 0.0). Advanced stages were more common among vulnerable subgroups, including males, older adults, rural residents, smokers, drinkers, individuals with obesity, lower education levels, and lower household incomes. This is the first study to investigate the long-term prevalence of CKM syndrome based on stages at the national level in an Asian population. Our findings emphasize the urgent need for tailored public health strategies targeting metabolic risk factors, particularly in vulnerable subgroups, to prevent progression to advanced CKM stages. National Research Foundation of Korea.

Background and Aims: Despite the potential association between herpes zoster infection and cardiovascular events, limited studies have investigated the relationship between live zoster vaccination and cardiovascular outcomes. This large-scale, population-based cohort study with a long-term follow-up aimed to investigate the association between live zoster vaccination and the risk of various cardiovascular events. Methods: Data on comprehensive information of individuals aged ≥50 years from South Korea (n = 2 207 784) were included from 1 January 2012, to 31 December 2021. National insurance information from the Korea Health Insurance Review and Assessment Service, the national health examination results from the Korean National Health Insurance Service, and the live zoster vaccination data from the Korea Disease Control and Prevention Agency were merged. The risk of incident cardiovascular outcomes after live zoster vaccination was assessed compared with unvaccinated individuals. The primary outcome was the risk of cardiovascular diseases based on International Classification of Diseases, Tenth Revision code diagnosis. In propensity score–based overlap weighted cohorts, Cox proportional hazard models were used to estimate hazard ratios (HRs) for overall and specific cardiovascular outcomes, while calculating restricted mean survival time (RMST) for each outcome. The observation period was from 1 January 2012, to 31 January 2024. Multiple stratification analyses were performed. Results: After applying propensity score–based overlap weighting, 1 271 922 individuals were included [mean age, 61.3 years (standard deviation, 3.4); 548 986 (43.2%) male; median follow-up time, 6.0 years] in overlap-weighted cohort. Live zoster vaccination was associated with lower risks of overall cardiovascular events [HR 0.77, 95% confidence interval (CI) 0.76–0.78], particularly major adverse cardiovascular events [0.74 (0.71–0.77)], heart failure [0.74 (0.70–0.77)], cerebrovascular disorders [0.76 (0.74–0.78)], ischaemic heart disease [0.78 (0.76–0.80)], thrombotic disorders [0.78 (0.74–0.83)], and dysrhythmia [0.79 (0.77–0.81)]. The RMST difference for overall cardiovascular events following live zoster vaccination was 95.14 days per decade (95% CI 94.99–95.30). The protective association persisted up to 8 years, with the greatest reduction observed 2–3 years post-vaccination. The decrease in cardiovascular disease risk was more pronounced among males, individuals aged <60 years, those with unhealthy lifestyle habits, and those from low-income households and rural residents. Conclusions: These findings suggest that live zoster vaccination may be beneficial as a public health strategy with potential implications for cardiovascular disease burden in the general population. This strategy may help address health disparities and mortality linked to cardiovascular complications.