Song JH, et al. J Korean Med Sci. 2022 Aug;37(33):e257. https://doi.org/10.3346/jkms.2022.37.e257

Kim SY, et al. Ann Occup Environ Med. 2023 Nov;35(1):e47. https://doi.org/10.35371/aoem.2023.35.e47

This study aimed to investigate whether working long hours was related to infertility among female Korean workers, while taking age into consideration. We used data from the 2018 National Survey on Fertility and Family Health and Welfare in Korea that is a cross-sectional, nationally representative, and population-based survey. Infertility was defined as women who were not pregnant after regular unprotected intercourse for a year. Working long hours was classified as ≥52 hours, and subgroups as per age were classified on the basis of being younger or older than 40 years of age. Differences in infertility risk between the long working hour group and none were estimated in crude and fully adjusted logistic regression models with age-group stratification. Of 5,909 Korean female workers, the crude and adjusted odds ratios (95% confidence intervals) of infertility for working long hours were 1.295 (0.948–1.737) and 1.303 (0.921–1.809), respectively. In the subgroup of patients below 40 years of age, the crude and adjusted odds ratios (95% confidence interval) were 1.957 (1.216–3.039) and 1.921 (1.144–3.120), whereas those aged 40 years or older had 0.994 (0.647–1.471) and 0.939 (0.560–1.501), respectively. The weighted prevalence of infertility increased as weekly working hours increased only for the younger than 40-year subgroup. Infertility is associated with working long hours, especially in young-aged workers. Thus, the working schedule must be structured to better suit young female workers.

Yang M, et al. Ann Occup Environ Med. 2023 Jul;35(1):e21. https://doi.org/10.35371/aoem.2023.35.e21

Park MY, et al. J Korean Med Sci. 2025 Jul;40:e224. https://doi.org/10.3346/jkms.2025.40.e224

Objectives: This study investigated the effects of hot and cold temperature on the renal function of people with chronic diseases, such as diabetes, hypertension, and chronic kidney disease, using large-scale clinical data. Methods: We used retrospective cohort data from the Clinical Data Warehouse of the Seoul St Mary’s Hospital, which contains clinical, diagnostic, laboratory, and other information about all patients who have visited the hospital since 1997. We obtained climate data from the Automated Synoptic Observing System of the Korea Meteorological Administration. The heat index was used as a measuring tool to evaluate heat exposure by indexing the actual heat that individuals feel according to temperature and humidity. The estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. To investigate changes in renal function trends with heat index, this study used generalized additive mixed models. Results: Renal function decreased linearly with increasing heat index after approximately 25°C, which was considered the flexion point of temperature. A linear decrease in the eGFR was observed with the effects of 0 to 5 lag days. Although there was a correlation observed between the decrease in eGFR and temperatures below −10°C, the results did not indicate statistical significance. Conclusions: The results of our study provide scientific evidence that high temperatures affect the renal function of people with chronic diseases. These results can help prevent heat-related morbidity by identifying those who are more likely to develop renal disease and experience worsening renal function.