The Korea National Health and Nutrition Examination Survey (KNHANES) is a national health survey mandated by Article 16 of the National Health Promotion Act to assess the health and nutritional status of the Korean population. Over the past 2 decades, the survey has continuously introduced timely survey components while strengthening its survey methodology and operational systems to enhance both the policy relevance and scientific utility of its findings. The 10th KNHANES (2025–2027) preserves the statistical representativeness of its sampling design while expanding the use of web-based self-administered questionnaires to improve participant convenience. In response to Korea’s transition into a super-aged society, the 10th KNHANES incorporates enhanced older-adult health surveys, including osteoporosis assessment and older adults’ life functioning, and newly introduces items addressing social support as part of the social determinants of health. In addition, a longitudinal follow-up survey system has been established to monitor long-term changes in population health. Collectively, these changes are expected to improve understanding of aging-related health issues, support evidence-based national health policy development, and expand the applicability of KNHANES data for academic research.

OBJECTIVES: Poor cardiovascular health (CVH) and the high prevalence of depressive symptoms represent significant public health concerns, underscoring the importance of examining their association. This study aimed to investigate the association between CVH, as defined by the American Heart Association’s 2022 Life’s Essential 8 (LE8) framework, and depressive symptoms. METHODS: This study used data from the 2014, 2016, 2018, and 2020 Korea National Health and Nutrition Examination Survey. Overall CVH, measured using LE8, was categorized into 3 groups: low score (0–<50), moderate score (50–<80), and high score (80–100). LE8 comprises 2 subdomains: health behaviors and health factors. Depressive symptoms were defined as a total score ≥10 on the Patient Health Questionnaire-9. Multiple logistic regression analyses were performed, adjusting for sex, age, socioeconomic status, and current drinking status. RESULTS: Among 17,294 adults, 257 male and 681 female reported significant depressive symptoms. Compared with individuals in the low LE8 category (reference), the odds ratio (OR) for depressive symptoms was 0.29 (95% confidence interval [CI], 0.21 to 0.40) for those in the high LE8 category. The OR for depressive symptoms was 0.39 (95% CI, 0.29 to 0.53) for individuals with a high health behavior score compared with those with a low health behavior score. In contrast, the health factor score was not significantly associated with depressive symptoms. CONCLUSIONS These findings suggest that overall CVH, particularly the health behavior subdomain, was associated with lower odds of depressive symptoms. Prospective longitudinal studies are warranted to validate these findings and clarify the directionality of the observed associations.

Confounding and the healthy worker survivor effect (HWSE) represent major methodological challenges in epidemiology, particularly in studies of low-dose exposures, where effect sizes are small and risk estimates can be readily distorted by bias. This systematic review aimed to summarize the methods used to adjust for confounding and the HWSE in studies of medical radiation workers. We systematically searched PubMed and Embase for studies of medical radiation workers from inception through June 30, 2025. Studies reporting excess risk estimates for any health outcomes associated with occupational radiation exposure were included. Study selection followed the PECO (Population, Exposure, Comparator, Outcome) criteria, and data were synthesized descriptively. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in PROSPERO (CRD42024589851). Sixteen eligible studies from 3 countries were identified, all of which were rated as high quality. To control for confounding, regression was used in all studies, followed by stratification (62.5%) and restriction (18.8%). Age, sex, and birth year were adjusted for in all models, with smoking being the next most frequently controlled variable. To mitigate the HWSE, only a single approach, adjustment for employment characteristics, was identified, and it was applied in 3 studies (18.8%). No other approaches, including restriction or g-methods, were employed. Although confounding is generally addressed using conventional analytical approaches, the HWSE has rarely been considered in studies of medical radiation workers. More comprehensive strategies that explicitly account for the HWSE are needed to improve the validity of risk estimates, particularly in low-dose occupational studies.

OBJECTIVES: The coronavirus disease 2019 (COVID-19) pandemic had direct effects on population health through infection and morbidity, as well as indirect effects on population mental health. We estimated the network structure of post-traumatic stress symptoms (PTSS) and depressive symptoms throughout the pandemic in Korea and aimed to identify the most central and bridging symptoms. METHODS: Participants aged 30–64 years completed mental health surveys across 3 phases of the COVID-19 pandemic: March 2020 (n=1,925), February–March 2021 (n=1,754), and December 2021–January 2022 (n=1,595). Using PTSS and depressive symptom data, we conducted network analyses, and the primary measures of symptom importance (centrality) were expected influence and bridge expected influence. RESULTS: In the comorbidity network, although the most central symptoms fluctuated over the course of the pandemic, sleep problems were consistently identified as the most influential bridge symptoms throughout. The symptom network structure differed between the subacute and chronic phases of the pandemic. CONCLUSIONS We found evidence of changes in the network structure of PTSS and depressive symptoms, even as sleep problems retained a consistent role as a bridging symptom. Although overall network structures varied across phases of the pandemic, the bridging role of sleep-related symptoms remained consistently strong, suggesting that sleep problems may represent a general and enduring mechanism underlying PTSS–depression comorbidity. During future pandemics, prompt screening for sleep problems may help prevent the development of comorbidity between PTSS and depressive symptoms.

OBJECTIVES: We evaluated the associations of smoking status, intensity, duration, and cumulative exposure with the risk of dental implant failure in Korean adults. METHODS: This retrospective cohort study utilized the National Health Insurance Service–Health Screening Cohort (2016–2019). Overall, 23,573 individuals who had completed the dental implant process were included. Smoking status was categorized as non-smoker, ex-smoker, or current smoker. Smoking intensity, duration, and cumulative exposure were classified using standardized thresholds (>10 cigarettes per day, >10 years, and >10 pack-years). Implant failure was defined as reimplantation or removal. Cox proportional hazards models were applied to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for demographic, clinical, and behavioral covariates. RESULTS: During follow-up, 605 implant failures occurred: 344 in non-smokers, 182 in ex-smokers, and 79 in current smokers. The corresponding incidence rates per 1,000 person-years were 11.56, 16.54, and 22.33, respectively. Current smoking was significantly associated with higher implant failure risk (adjusted HR, 1.59; 95% CI, 1.20 to 2.09), while ex-smokers displayed a non-significant increase (adjusted HR, 1.16; 95% CI, 0.94 to 1.45). A dose–response relationship was observed: smoking more than 10 cigarettes per day, smoking for more than 10 years, or exceeding 10 pack-years was associated with significantly increased risk. CONCLUSIONS Smoking is a significant, dose–dependent risk factor for dental implant failure in Korean adults. Current smokers have the highest risk; smoking cessation may reduce adverse outcomes. These findings emphasize the importance of detailed smoking assessments and cessation counseling in implant care and public health strategies.

Varicella, caused by the varicella-zoster virus, was once nearly universal in childhood before the advent of vaccination and may lead to severe complications and even fatalities. Monitoring varicella vaccine effectiveness is crucial yet often overlooked in settings with limited surveillance infrastructure. The Korean Varicella Immunization Monitoring (K-VIM) Scheme was established to address this gap by assembling a national, insurance-based birth cohort of children born between 2011 and 2022 (n=4,505,165). This cohort leverages comprehensive healthcare databases in Korea to capture vaccination records, medical visits, and varicella infection outcomes for virtually all children within the target birth years. We describe the enrollment and key characteristics of the K-VIM cohort, including vaccination coverage, demographic features, and varicella incidence to date. The structure and completeness of Korea’s national health insurance and immunization registries enable robust longitudinal tracking of varicella infections among vaccinated versus unvaccinated children. Early findings demonstrate distinct patterns in infection rates and disease severity according to vaccination status. The K-VIM Scheme provides a foundation for ongoing epidemiological studies of varicella vaccine effectiveness and public health impact in Korea. Future plans include evaluating the long-term effects of varicella vaccination, including potential impacts on herpes zoster incidence, using diverse study designs to strengthen causal inference and inform immunization policy.

OBJECTIVES: This mixed-methods observational study aimed to examine the temporal relationship between trends in cigarette smoking prevalence and lung cancer mortality and incidence rates, and to estimate the latency period between smoking initiation and lung cancer diagnosis among smokers at the individual level. METHODS: Smoking prevalence data for 1960–2022 were reconstructed using data from the Korea National Health and Nutrition Examination Survey (1998–2022). Lung cancer mortality data (1983–2022) and incidence data (1999–2022) were obtained from Statistics Korea and the Korea Central Cancer Registry. The population latency period was estimated using peak comparison and distributed lag non-linear models. The individual latency period was estimated as the average time interval between age at smoking initiation and age at lung cancer diagnosis using individual-level data from the National Health Insurance Service cohort. RESULTS: In men, smoking prevalence peaked around 1985, whereas lung cancer mortality peaked around 2000 during 1960–2022, indicating a lag time of approximately 15 years. In women, lung cancer mortality peaked in 2002, while smoking prevalence peaked around the same time. The population-level latency period between smoking and lung cancer incidence was estimated to be 15 years after adjustment for age, gender, and year of outcome. The individual latency period was estimated to be 42.6 years (standard deviation [SD], 12.5) in men and 34.4 years (SD, 14.2) in women. Smoking intensity and age at initiation did not appear to shorten the individual latency period. CONCLUSIONS Estimates of the smoking-attributable lung cancer burden should account for historical smoking prevalence from approximately 15 years earlier.

OBJECTIVES: Individuals with disabilities are at greater risk of hospitalization than the general population. We examined 10-year trends in potentially preventable hospitalizations (PPH) in Korea, comparing individuals with and without disabilities and assessing age-specific patterns. METHODS: Using National Health Information Database claims data (2010–2019), we established a fixed cohort of newly registered individuals with disabilities and control subjects statistically matched (1:1.5) at baseline. Annual PPH rates among patients with each condition were calculated and age- and sex-standardized according to Organization for Economic Cooperation and Development Health Care Quality Indicators definitions. Trends and annual percent changes (APCs) were analyzed by disability status and age group (non-older: 30–64; older adults: ≥65 years). RESULTS: Between 2010 and 2019, PPH rates declined significantly in both groups. Among individuals with disabilities, the steepest decline was observed for hypertension (APC, −15.7%; 95% confidence interval [CI], −17.7 to −13.7), whereas congestive heart failure showed the largest reduction among individuals without disabilities (APC, −7.8%; 95% CI, −10.8 to −4.7). Declines were generally greater among non-older adults aged 30–64 years, regardless of disability status. The disparity between disability and non-disability groups narrowed over the decade, primarily due to larger improvements among non-older adults. Older adults with disabilities consistently exhibited the highest PPH rates for most conditions, whereas younger individuals with disabilities had the highest rates for diabetes. CONCLUSIONS PPH rates declined over the decade among both individuals with and without disabilities, particularly for hypertension and among non-older adults. However, older adults with disabilities remain at elevated risk, underscoring the need for targeted strategies to improve access to community-based primary care.

OBJECTIVES: For employees, work-time control (WTC) may protect against burnout and turnover. However, evidence from Korean workplaces is limited. This study aimed to examine whether WTC is associated with burnout and turnover intention and to test whether burnout mediates this relationship. METHODS: We analyzed data from 4,745 wage workers in the 2024 wave of the Korean Work, Sleep, and Health Study. WTC was assessed across 6 domains, burnout was measured using the Korean Burnout Syndrome Scale, and turnover intention was assessed using a validated 4-item scale. Logistic regression was used to estimate the associations of WTC quartile with burnout and turnover intention, and mediation analysis was used to decompose the association between WTC and turnover intention through burnout. RESULTS: Among 4,745 workers, the prevalence of burnout was 3.9% and turnover intention was 34.5%; both increased stepwise across lower WTC quartiles. In adjusted models, workers in the lowest WTC quartile had higher odds of burnout (odds ratio [OR], 3.95; 95% confidence interval [CI], 2.41 to 6.47) and turnover intention (OR, 2.24; 95% CI, 1.85 to 2.71) than those in the highest quartile. Mediation analysis showed that burnout explained 36.6% (95% CI, 22.3 to 51.0) of the association between WTC and turnover intention. CONCLUSIONS Lower WTC was linked to higher burnout and turnover intention, with burnout explaining more than one-third of this relationship.

OBJECTIVES: This study aimed to evaluate a fixed-duration algorithm for gestational age (GA) estimation according to pregnancy outcomes and to describe the GA distribution of pregnancy-related codes in Korea. METHODS: We included 351,055 pregnancy episodes (2019–2022) from linked data between the National Health Insurance Service and the Korea Immunization Registry Information System (KIRIS). GA from claims data was estimated by subtracting fixed durations from the delivery date (algorithm-based GA), and GA derived from KIRIS was defined as the gold standard. Accuracy was evaluated as the proportion of episodes in which the difference between the estimated GA and the reference standard fell within ±2 weeks. We described the distributions of the GA at which each prenatal test, pregnancy complication, and diagnostic code was recorded. RESULTS: Algorithm-based GA estimation showed high accuracy for live births (92.2% within ±2 weeks) but markedly lower accuracy for non-live birth outcomes, including stillbirth (3.3%), termination (7.2%), spontaneous abortion (45.2%), and ectopic pregnancy (20.0%). In additional analyses aimed at identifying potential indicators for improving GA estimation, most events occurred within clinically expected timeframes, although some individual codes exhibited poor temporal alignment. CONCLUSIONS Algorithm-based GA estimation using claims data performed well for live births but demonstrated limited accuracy for non-live birth outcomes. Incorporating information from prenatal tests and pregnancy complications may enhance GA estimation.