Background
Insulin resistance contributes to the development of cardiovascular disease and type 2 diabetes mellitus. Smoking leads to an increase in triglyceride levels, which, in turn, increases insulin resistance. Although the number of e-cigarette users has increased in recent years, few studies have investigated the association between ecigarette use and insulin resistance. Therefore, this study aimed to determine the association between e-cigarette use and insulin resistance using the triglyceride-glucose (TyG) index in Korean adults.
Methods
This study included 4,404 healthy adults aged ≥20 years who participated in the Korea National Health and Nutrition Examination Survey between 2019 and 2020. Participants were categorized as never-smokers or ecigarette users, and the TyG index was categorized into low- and high-TyG index groups according to the median value (9.22). A logistic regression analysis was performed to determine the association between e-cigarette smoking and insulin resistance.
Results
E-cigarette users had a higher TyG index than never smokers (e-cigarette: mean=3.95; never: mean=9.18; P<0.001). The e-cigarette users had a higher risk of being in the high TyG index group than never-smokers (odds ratio [OR], 1.38; 95% confidence interval [CI], 1.03–1.84). In the subgroup analysis stratified by sex, age, and body mass index, a higher OR for a high TyG index was observed in men (OR, 1.46; 95% CI, 1.03–2.08) and individuals aged 60 years or older (OR, 3.74; 95% CI, 1.14–12.30).
Conclusion
Our findings suggest that e-cigarette use is significantly associated with insulin resistance.

Background
Skipping breakfast is associated with an increased risk of chronic inflammatory diseases. This study aimed to examine the association between breakfast-eating habits and inflammation, using high-sensitivity C-reactive protein (hs-CRP) as a marker.
Methods
A total of 4,000 Korean adult males with no history of myocardial infarction, angina, stroke, diabetes, rheumatoid arthritis, cancer, or current smoking were included. Data from the 2016–2018 Korea National Health and Nutrition Examination Survey were used for analysis. The frequency of breakfast consumption was assessed through a questionnaire item in the dietary survey section asking participants about their weekly breakfast consumption routines over the past year. Participants were categorized into two groups, namely “0–2 breakfasts per week” and “3–7 breakfasts per week”; hs-CRP concentrations were measured through blood tests.
Results
Comparing between the “infrequent breakfast consumption (0–2 breakfasts per week)” and “frequent breakfast consumption (3–7 breakfasts per week)” groups, the mean hs-CRP was found to be significantly higher in the “infrequent breakfast consumption” group, even after adjusting for age, body mass index, physical activity, alcohol consumption, systolic blood pressure, blood pressure medication, fasting blood glucose, and triglycerides (mean hs-CRP: frequent breakfast consumption, 1.36±0.09 mg/L; infrequent breakfast consumption, 1.17±0.05 mg/L; P-value=0.036).
Conclusion
Less frequent breakfast consumption was associated with elevated hs-CRP levels. Further large-scale studies incorporating adjusted measures of daily eating patterns as well as food quality and quantity are required for a deeper understanding of the role of breakfast in the primary prevention of chronic inflammatory diseases.

Background
Sleep duration is associated with hearing loss, especially presbycusis, which is the most common type of hearing loss; however, there is limited evidence regarding this association among the Korean population. We aimed to determine the relationship between sleep duration and high-frequency hearing loss in Korean adults aged ≥40 years.
Methods
We examined 5,547 Korean adults aged ≥40 years who completed audiometric tests and questionnaires regarding sleep duration during the 2010–2012 cycle of the Korea National Health and Nutrition Examination Survey. Mild presbycusis was defined as >25 decibels (dB) and <40 dB, whereas moderate-to-severe presbycusis was defined as >40 dB pure tone averages at high frequencies (3,000, 4,000, and 6,000 Hz) for both ears. Additionally, the sleep duration was divided into quartiles. Odds ratios and 95% confidence intervals were estimated using multivariable logistic regression after adjusting for covariates.
Results
The prevalence of presbycusis in South Korean adults was 62.1%, of which 61.4% showed moderate to severe presbycusis. The incidence of moderate-to-severe, but not mild, presbycusis showed a significant positive correlation with sleep duration.
Conclusion
Our findings suggest that sleep duration is associated with the prevalence of presbycusis.

Citations

• Joint association of sleep duration and depression with new-onset hearing loss: a national cohort study
  Fang Wang, Yu-Jun Xiong, Da-Ming Shao, Tian Lv, Shiqin Chen, Qian-Yuan Zhu
  Frontiers in Nutrition.2025;[Epub]     CrossRef
• Sleep characteristics and hearing loss in middle-aged and older adults: The National Health and Nutrition Examination Survey 2015–2018
  Kening Jiang, Adam P. Spira, Nicholas S. Reed, Frank R. Lin, Jennifer A. Deal
  Sleep Epidemiology.2024; 4: 100082.     CrossRef
• Age-related hearing loss and its potential drug candidates: a systematic review
  Shiyu Hu, Qingru Sun, Fei Xu, Ninghua Jiang, Jianli Gao
  Chinese Medicine.2023;[Epub]     CrossRef

Background
Folic acid is involved in inflammatory reactions; however, the association between folic acid and allergic diseases, particularly asthma, remains unclear. Thus, this study aimed to evaluate the association between serum folic acid levels and asthma in Koreans.
Methods
This study analyzed the serum folic acid levels of 6,615 individuals included in the 2016–2018 Korea National Health and Nutrition Examination Survey. The prevalence of asthma was determined using a questionnaire that identified cases of physician-diagnosed asthma. The relationship between serum folic acid levels and asthma was analyzed using logistic regression analysis.
Results
Multiple logistic regression analysis showed that a 1 ng/mL increase in serum folic acid level significantly reduced the risk of asthma after adjusting for confounding factors including sex, age, household income, current smoking, current alcohol use, and body mass index (odds ratio [OR], 0.930; 95% confidence interval [CI], 0.876– 0.987; P=0.017). The relationship between the adjusted odds of asthma and serum folic acid levels were consistently inverse (OR, 2.266; 95% CI, 1.126–4.420; P for trend=0.038).
Conclusion
Serum folic acid levels are inversely associated with physician-diagnosed asthma in the Korean population.

Citations

• Association between serum folate levels and blood eosinophil counts in American adults with asthma: Results from NHANES 2011–2018
  Jun Wen, Changfen Wang, Mohan Giri, Shuliang Guo
  Frontiers in Immunology.2023;[Epub]     CrossRef

Background
The aim of this study was to evaluate the association between near work time and depression.
Methods
Data of 1,551 workers aged 19–49 years from the sixth Korea National Health and Nutrition Examination Survey were examined. The Patient Health Questionaire-9 scores were used to screen for depression. Participants who scored a total of 10 or above, which is suggestive of the presence of depression, were classified as the depression group; the rest were classified as normal. The correlation between daily near work time and depression was analyzed using multivariate logistic analysis after adjusting for other sociodemographic and health behavior-related variables.
Results
Multivariate logistic analysis found that workers with 3 or more hours of near work were more likely to report depression compared to the reference group who had 2 or fewer hours per day of near work (adjusted odds ratio, 2.471; 95% confidence interval, 1.062–5.747).
Conclusion
Longer near work time was associated with depression among South Korea’s workers. Therefore, it is necessary to reduce near work time to prevent depression.

Background
BMI alone may not serve as an index of obesity because it does not reflect body composition. The present study aimed to compare arterial stiffness as assessed by the brachial-ankle pulse wave velocity (ba-PWV) among groups defined by body fat percentage (pBF) and BMI.
Methods
This cross-sectional study was based on 1,700 participants (1,044 men and 656 women) who completed a health screening examination at a national hospital between January 2011 and February 2016. Participants were divided into four groups according to BMI and pBF: normal fat and normal weight (NFNW); excessive fat and normal weight (EFNW); normal fat and obese (NFO); and excessive fat and obese (EFO). The ba-PWV and other cardiometabolic factors were compared among the four groups in men and women separately.
Results
For both sexes, the NFNW group had a lower metabolic risk compared to that in the other groups (EFNW, NFO, and EFO). After adjusting for multiple variables, the NFO males had a significantly lower ba-PWV compared to those in the other groups, including NFNW males. The NFO group had significantly more skeletal muscle mass and muscle mass compared the other groups (P<0.05). Among women, the NFNW group had a significantly lower ba-PWV compared the other groups, even after adjusting for multiple variables.
Conclusion
Lower pBF in obese men may be associated with improved cardiovascular risk.

Citations

• Improved fatty acid profile reduces body fat and arterial stiffness in obese adolescents upon combinatorial intervention with exercise and dietary restriction
  Lei Xu, Xiaoyu Zou, Zhiqiang Gao, Caifeng Mao, Hang Su, Chunyan Li, Ning Chen
  Journal of Exercise Science & Fitness.2021; 19(4): 234.     CrossRef
• Borderline-High Mean Corpuscular Volume Levels Are Associated with Arterial Stiffness among the Apparently Healthy Korean Individuals
  Haneul Kwon, Byoungjin Park
  Korean Journal of Family Medicine.2020; 41(6): 387.     CrossRef