Risk Factors for Musculoskeletal Disorders in Korean Farmers: Survey on Occupational Diseases in 2020 and 2022.

Background/objectives: This study investigated factors influencing the prevalence of musculoskeletal disorders (MSDs) resulting from agricultural work, utilizing the 2020 and 2022 occupational disease survey data collected by the Rural Development Administration. The combined data from these years indicated a 6.02% prevalence of MSDs, reflecting a significant class imbalance in the binary response variables.

Obesity-Status-Linked Affecting Factors of Dyslipidemia in Korean Young-Adult Men: Based on the Korea National Health and Nutrition Examination Survey (2019-2021).

In recent years, there has been a growing trend of obesity and dyslipidemia among young adult men in South Korea. Therefore, we aimed to identify the obesity-related factors of dyslipidemia among young adult men in Korea using 3-year data (2019-2021) from the 8th Korea National Health and Nutrition Examination Survey. We included 1559 eligible men aged 19-39 years and examined the association between dyslipidemia and participants' general characteristics, health-related characteristics, and food intake according to obesity status.

Prognosis and recurrence patterns in patients with early stage lung cancer: a multi-state model approach.

Background: We aimed to assess whether recurrence patterns affect survival and to use a multi-state model to predict the prognosis of early stage non-small cell lung cancer in patients who underwent surgical resection.

Methods: Patients with early stage non-small cell lung cancer who underwent surgical resection at two tertiary medical centers between 2010 and 2015 were retrospectively analyzed. A multi-state model was employed with one initial state (surgery), two intermediate states (locoregional recurrence, distant metastasis), and one absorbing state (death), comprising five transitions: surgery to locoregional recurrence, surgery to distant metastasis, surgery to death without recurrence, locoregional recurrence to death, and distant metastasis to death.

Effect of Perceived Stress on Health-Related Quality of Life among Primary Caregiving Spouses of Patients with Severe Dementia: The Mediating Role of Depression and Sleep Quality.

Recently, there has been a rise in the number of spouses becoming primary caregivers to patients with dementia. This study identifies the mediating effects of depression and sleep quality on the relationship between perceived stress and health-related quality of life (HRQoL) among primary caregiving spouses of patients with severe dementia through a secondary data analysis of the 2018 Korea Community Health Survey by the Korea Disease Control and Prevention Agency. Data from 229 primary caregiving spouses of patients with severe dementia were analyzed using descriptive statistics, Spearman's rank correlation or Pearson's correlation analysis, and the lavaan R package, version 0.

The Value of the Illness-Death Model for Predicting Outcomes in Patients with Non-Small Cell Lung Cancer.

Purpose: The illness-death model (IDM) is a comprehensive approach to evaluate the relationship between relapse and death. This study aimed to illustrate the value of the IDM for identifying risk factors and evaluating predictive probabilities for relapse and death in patients with non-small cell lung cancer (NSCLC) in comparison with the disease-free survival (DFS) model.

Materials And Methods: We retrospectively analyzed 612 NSCLC patients who underwent a curative operation.

Predictors of Cognitive Function in Community-Dwelling Older Adults by Age Group: Based on the 2017 National Survey of Older Korean Adults.

Owing to a growing older adult population, dementia is emerging as an important health issue. Given that maintaining cognitive functions is crucial for the prevention of dementia, this study aimed to identify the predictors of cognitive function in community-dwelling older adults, through a secondary data analysis of the 2017 National Survey of Older Koreans. A total of 9836 participants were classified into three age groups-young-old (65-74 years), old-old (75-84 years), and oldest-old (≥85 years)-and were separately analyzed using multiple linear regression models.

Assessing the Optimal Cutpoint for Tumor Size in Patients with Lung Cancer Based on Linear Rank Statistics in a Competing Risks Framework.

Purpose: In clinical studies, patients may experience several types of events during follow up under the competing risks (CR) framework. Patients are often classified into low- and high-risk groups based on prognostic factors. We propose a method to determine an optimal cutpoint value for prognostic factors on censored outcomes in the presence of CR.

Additive-multiplicative hazards regression models for interval-censored semi-competing risks data with missing intermediate events.

Background: In clinical trials and survival analysis, participants may be excluded from the study due to withdrawal, which is often referred to as lost-to-follow-up (LTF). It is natural to argue that a disease would be censored due to death; however, when an LTF is present it is not guaranteed that the disease has been censored. This makes it important to consider both cases; the disease is censored or not censored.

Comparing survival functions with interval-censored data in the presence of an intermediate clinical event.

Background: In the presence of an intermediate clinical event, the analysis of time-to-event survival data by conventional approaches, such as the log-rank test, can result in biased results due to the length-biased characteristics.

Methods: In the present study, we extend the studies of Finkelstein and Nam & Zelen to propose new methods for handling interval-censored data with an intermediate clinical event using multiple imputation. The proposed methods consider two types of weights in multiple imputation: 1) uniform weight and 2) the weighted weight methods.

A review on mathematical models for estimating indoor radon concentrations.

Radiation from natural sources is one of causes of the environmental diseases. Radon is the leading environmental cause of lung cancer next to smoking. To investigate the relationship between indoor radon concentrations and lung cancer, researchers must be able to estimate an individual's cumulative level of indoor radon exposure and to do so, one must first be able to assess indoor radon concentrations.

A comparative study on gene-set analysis methods for assessing differential expression associated with the survival phenotype.

Background: Many gene-set analysis methods have been previously proposed and compared through simulation studies and analysis of real datasets for binary phenotypes. We focused on the survival phenotype and compared the performances of Gene Set Enrichment Analysis (GSEA), Global Test (GT), Wald-type Test (WT) and Global Boost Test (GBST) methods in a simulation study and on two ovarian cancer data sets. We considered two versions of GSEA by allowing different weights: GSEA1 uses equal weights, yielding results similar to the Kolmogorov-Smirnov test; while GSEA2's weights are based on the correlation between genes and the phenotype.

Median regression model with interval censored data.

Quantile regression methods have been used to estimate upper and lower quantile reference curves as the function of several covariates. Especially, in survival analysis, median regression models to the right-censored data are suggested with several assumptions. In this article, we consider a median regression model for interval-censored data and construct an estimating equation based on weights derived from interval-censored data.

A generalized log-rank-type test for comparing survivals with doubly interval-censored data.

In doubly interval-censored data, the survival time of interest is defined as the elapsed time between an initial event and a subsequent event, but the occurrences of both events cannot be observed exactly. Instead, only right- or interval-censored observations on the occurrence times are available. Our purpose is to develop a generalized log-rank-type test for comparing survival functions of several groups.

Cost-effective mammography screening in Korea: high incidence of breast cancer in young women.

The epidemiological characteristics of breast cancer in Korean women are different from the characteristics reported in Western women. The highest incidence rate occurs in Korean women in their 40s. The purpose of this study was to determine the most cost-effective screening interval and target age range for Korean women from the perspective of the national healthcare system.

Scheduling mammography screening for the early detection of breast cancer in Korean women.

Objective: To propose an efficient screening schedule for breast cancer among Korean women using the stochastic model in which the age-specific incidence rate was considered.

Setting: Female breast cancer data in the Korea Central Cancer Registry 2002.

Methods: The stochastic model was based on the threshold method, in which the schedule is determined by a pre-specified threshold value.

Haplotype-based score test for linkage in nuclear families.

Background: To look for genetic linkage between angiotensin-I converting enzyme(ACE) gene and hypertension in a Korean adolescent cohort, we developed a powerful test using the covariances between marginal differences and their variances in a transmission/non-transmission table.

Results: We estimated haplotype frequencies using the parental and affected offspring's genotypes and then constructed a transmission/non-transmission table for the parental haplotypes transmitted to the offspring. We then proposed a test for checking the marginal homogeneity in the table.

[A study on scheduling periodic examinations for the early detection of breast cancer in Korea].

Objectives: The purposes of this study were to propose a screening schedule for the early detection of breast cancer among Korean women, as based on the statistical model, and to compare the efficacy of the proposed screening schedule with the current recommendations.

Methods: The development of the screening schedule for breast cancer closely followed the work of Lee and Zelen (1998). We calculated the age-specific breast cancer incidence rate from the Korea Central Cancer Registry (2003), and then we estimated the scheduling of periodic examinations for the early detection of breast cancer, using mammography, and based on the threshold method.

Statistical algorithm in genetic linkage based on haplotypes.

Objectives: This study was conducted to propose a new transmission/disequilibrium test (TDT) to test the linkage between genetic markers and diseasesusceptibility genes based on haplotypes. Simulation studies were performed to compare the proposed method with that of Zhao et al. in terms of type I error probability and powers.

Nonparametric quantile estimation with correlated failure time data.

In biomedical studies, correlated failure time data arise often. Although point and confidence interval estimation for quantiles with independent censored failure time data have been extensively studied, estimation for quantiles with correlated failure time data has not been developed. In this article, we propose a nonparametric estimation method for quantiles with correlated failure time data.