Background
The liver plays an important role in gonadal steroid hormone metabolism, which can affect reproductive health, including the menstrual cycle. However, evidence from large population-based studies is limited. Therefore, this study aimed to investigate the association between liver function markers and menstrual cycle irregularities in premenopausal Korean women using nationwide data.
Methods
This study analyzed Data from the Korea National Health and Nutrition Examination Survey 2010–2011. We investigated 3,045 premenopausal women aged 19–59 years. Liver function markers including serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase, and fatty liver index were analyzed. Multivariable logistic regression analysis was performed to investigate the association between liver function markers and menstrual cycle irregularity while adjusting for confounding factors. Values were presented as odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup analysis was also performed.
Results
Baseline characteristic analysis showed that approximately 14.4% of the study population experienced menstrual cycle irregularity. The mean age was 34.5±0.7 years. The highest quartile of serum ALT and AST levels showed significantly higher ORs for menstrual cycle irregularity (adjusted OR, 1.83; 95% CI, 1.26–2.64 and adjusted OR, 1.67; 95% CI, 1.17–2.39, respectively). A similar result was observed in the subgroup analysis.
Conclusion
Liver function markers were positively associated with menstrual cycle irregularities. In clinical settings, women of reproductive age with relatively decreased liver function should be considered for regular followup of their reproductive health status.

Background
Although the association between smoking and health-related quality of life (HRQoL) has been established, the effects of tobacco products, including combustible cigarettes (CCs) and non-combustible nicotine or tobacco products (NNTPs), on HRQoL remain unclear. This study examined the association between tobacco use and HRQoL in Korean men.
Methods
Data from the Korea National Health and Nutrition Examination Survey conducted between 2013 and 2020 were analyzed. A total of 16,429 male participants aged ≥19 years completed the European Quality of Life-5 Dimensions (EQ-5D). Impaired HRQoL was defined as scoring in the lowest 20% of the EQ-5D index and having some or extreme problems in the following five domains of the EQ-5D: mobility, self-care, usual activities, pain/ discomfort, and anxiety/depression. Multiple logistic regression was conducted to evaluate the risk of impaired HRQoL in current tobacco users.
Results
Current tobacco users exhibited a significantly higher risk of impaired HRQoL compared with never users (odds ratio [OR], 1.42; 95% confidence interval [CI], 1.05–1.92). Compared to never users, current tobacco users reported more problems with mobility and pain/discomfort (all P<0.05). Moreover, compared with former tobacco users, current tobacco users had a higher risk of impaired HRQoL (OR, 1.60; 95% CI, 1.18–2.17). Compared to former tobacco users, current tobacco users reported more problems with mobility and pain/discomfort (all P<0.05).
Conclusion
Use of CCs and NNTPs is associated with impaired HRQoL in Korean men. Therefore, further interventions for lifestyle modification and smoking cessation treatments are required to reduce the risk of impaired HRQoL among current tobacco users.