Background Circadian rhythm disturbance caused by shift work has adverse effects on the metabolic homeostasis of the liver. Disruption of the metabolic homeostasis of the liver causes fat accumulation in the liver. The aim of this study was to investigate the correlation between shift work and non-alcoholic fatty liver disease (NAFLD) among male workers in the steel manufacturing industry of Korea. Methods Based on medical examination data collected in June 2020, 2,511 male subjects from one steel manufacturing company in Korea were selected in total. NAFLD was evaluated using abdominal ultrasound, which was performed by two experienced radiologists. The multinomial logistic regression analysis was performed by adjusting for age, physical activity, smoking history, alcohol consumption, body mass index, waist circumference, blood pressure, blood glucose, lipidemia, liver function test, employment duration, and hepatotoxic materials exposure status. Results Compared to daytime workers, the odds ratio (OR) of moderate-severe NAFLD in shift workers was 1.449 (95% confidence interval [CI], 1.028–2.043). Compared to daytime workers, the ORs of moderate-severe NAFLD were significantly higher for the group that engaged in total shift work for more than 20 years (OR, 2.285; 95% CI, 1.051–4.970), the group that was not allowed to sleep during night shift work (OR, 1.463; 95% CI, 1.030–2.078), and the group that consumed food during night shift work (OR, 1.580; 95% CI, 1.093–2.284). Conclusions There was a correlation between shift work and moderate-severe NAFLD in male steel manufacturing workers. There will be a need for more research related to the correlation of shift work with steatohepatitis and cirrhosis in the future.

Background This study aimed to investigate the association between lead exposure and serum gamma-glutamyl transpeptidase (γGT) levels as an oxidative stress marker in male steelworkers. Methods Data were collected during the annual health examination of workers in 2020. A total of 1,654 steelworkers were selected, and the variables for adjustment included the workers’ general characteristics, lifestyle, and occupational characteristics. The association between the blood lead level (BLL) and serum γGT level was investigated by multiple linear and logistic regression analyses. The BLL and serum γGT values that were transformed into natural logarithms were used in multiple linear regression analysis, and the tertile of BLL was used in logistic regression analysis. Results The geometric mean of the participants’ BLLs and serum γGT level was 1.36 μg/dL and 27.72 IU/L, respectively. Their BLLs differed depending on age, body mass index (BMI), smoking status, drinking status, shift work, and working period, while their serum γGT levels differed depending on age, BMI, smoking status, drinking status, physical activity, and working period. In multiple linear regression analysis, the difference in models 1, 2, and 3 was significant, obtaining 0.326, 0.176, and 0.172 (all: p < 0.001), respectively. In the multiple linear regression analysis stratified according to drinking status, BMI, and age, BLLs were positively associated with serum γGT levels. Regarding the logistic regression analysis, the odds ratio of the third BLL tertile in models 1, 2, and 3 (for having an elevated serum γGT level within the first tertile reference) was 2.74, 1.83, and 1.81, respectively. Conclusions BLL was positively associated with serum γGT levels in male steelworkers even at low lead concentrations (< 5 μg/dL).

Background Perfluoroalkyl substances (PFAS) are chemicals widely used in various products in everyday life. Due to its unique strong binding force, the half-life of PFAS is very long, so bioaccumulation and toxicity to the human body are long-standing concerns. In particular, effects on kidney function have recently emerged and there are no studies on the effect of PFAS on kidney function through epidemiological investigations in Korea. From 2018 to 2020, the Korean National Environmental Health Survey (KoNEHS) cycle 4, conducted an epidemiological investigation on the blood concentration of PFAS for the first time in Korea. Based on this data, the relationship between PFAS blood concentration and kidney function was analyzed for adolescents. Methods We investigated 5 types of PFAS and their total blood concentration in 811 middle and high school students, living in Korea and included in KoNEHS cycle 4, and tried to find changes in kidney function in relation to PFAS concentration. After dividing the concentration of each of the 5 PFAS and the total concentration into quartiles, multivariable linear regression was performed to assess the correlation with kidney function. The bedside Schwartz equation was used as an indicator of kidney function. Results As a result of multivariable linear regression, when observing a change in kidney function according to the increase in the concentration of each of the 5 PFAS and their total, a significant decrease in kidney function was confirmed in some or all quartiles. Conclusions In this cross-sectional study of Korean adolescents based on KoNEHS data, a negative correlation between serum PFAS concentration and kidney function was found. A well-designed longitudinal study and continuous follow-up are necessary.

Background Haenyeo is a woman who has the job of collecting seafood in the Jeju Sea at an average temperature of 13°C–14°C. The purpose of this study was to examine the cold acclimatization and occupational characteristics of Haenyeo through biomarkers such as orexin and irisin related to heat generation in the body. Methods Twenty-one Haenyeo and 25 people with similar age, body type, and body mass index were selected as the control group (Control G). In the cold exposure experiment, a climate chamber was set to 5°C and both feet were immersed in a 15°C water tank for 30 minutes. Tympanic temperature (T ty ) and skin temperature (T sk ) were measured, and the mean body temperature (mT b ) was calculated. Blood samples were collected before and immediately after the examination. Orexin and irisin levels were analyzed. Results Orexin levels were elevated after cold stimulation from 12.17 ± 4.44 to 12.95 ± 4.53 ng/mL (Haenyeo group [Haenyeo G], p < 0.01) and 10.37 ± 3.84 to 11.25 ± 4.02 ng/mL (Control G, p < 0.001). Irisin levels were elevated after cold stimulation from 4.83 ± 2.28 to 5.36 ± 2.23 ng/mL (Haenyeo G, p < 0.001) and 3.73 ± 1.59 to 4.18 ± 2.04 ng/mL (Control G, p < 0.001). The difference between Haenyeo G and Control G values in orexin and irisin appears not only in pre-exposure but also in post-exposure ( p < 0.05). Conclusions Our experimental results suggest that Haenyeo G were relatively superior in cold tolerance to Control G under cold exposure conditions. Haenyeo’s cold acclimatization is due to the basic differences in pyrogens regarding body temperature control such as orexin and irisin. This means that Haenyeo are advantageous for cold survival.

Background The purpose of this study is to investigate the relationship between job stress and impaired fasting glycemia (IFG) of male workers in a manufacturing industry. Methods Data were collected from 5,886 male workers in a manufacturing industry who participated in the medical examination from June 19 to August 14, 2020 through self-reported questionnaires. The general characteristics of the subjects, shift work, high blood pressure, dyslipidemia, and job stress were included. Job stress was measured using the Korean Occupational Stress Scale (KOSS) consisting of 8 items and 43 questions. Multivariable logistic regression analysis was used to investigate the IFG association with job stress. Results Among the various factors that can cause job stress, only high job demand was associated with a risk of IFG (odds ratio, 1.43; 95% confidence interval, 1.13–1.82) especially in non-shift worker. For all other factors, no statistically significant results were obtained. Conclusions In this study of male workers engaged in the Korean steel manufacturing industry, the 'job demand' item among job stress of non-shift worker was related to IFG.