Association between long working hours and metabolic dysfunction-associated steatotic liver disease: a nationwide population-based study in Korea.

OBJECTIVES: Long working hour is a known risk factor for metabolic diseases. We explored the association between working hours and metabolic dysfunction-associated steatotic liver disease (MASLD). STUDY DESIGN: Data on working hours among 22,818 workers (11,999 females) from the Korea National Health and Nutrition Examination Survey (2013-2021) were used for this study. METHODS: MASLD was defined as a combination of hepatic steatosis combined with one or more of cardiometabolic risk factors (overweight/obesity, prediabetes/diabetes, raised blood pressure, hypertriglyceridemia, low high-density lipoprotein cholesterol). Hepatic steatosis was assessed using the hepatic steatosis index. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: The overall prevalence of MASLD was 30.4% in men and 18.1% in women. Among male workers, 20.2% worked ≥55 h/week, whereas among female workers, 10.1% worked ≥55 h/week. Compared with working 35-40 h/week, working ≥55 h/week was positively associated with overweight/obesity (OR: 1.21; 95% CI: 1.05-1.40), pre-diabetes mellitus (pre-DM)/DM (OR: 1.20; 95% CI: 1.04-1.38), raised blood pressure (OR: 1.17; 95% CI: 1.02-1.35), and presence of any cardiometabolic risk factors (OR: 1.56; 95% CI: 1.21-2.02). The adjusted OR (95% CI) of the association between working hours and MASLD was 1.27 (1.09-1.47) for ≥55 h/week compared with working 35-40 h/week in male workers. In female workers, long working hours were not clearly associated with cardiometabolic risk factors and MASLD. CONCLUSION: Long working hours are positively associated with MASLD among Korean male workers. Policy interventions are needed to mitigate the adverse metabolic effects of prolonged working hours.

Association between social jetlag and leisure-time physical activity and muscle strengthening exercise in young adults: findings from a nationally representative sample in South Korea.

OBJECTIVES: Social jetlag (SJL), which is characterised by a misalignment between biological and social time, is associated with cardiometabolic risk factors. This study investigated the relationship between SJL, leisure-time physical activity (LTPA) and muscle strengthening exercise (MSE) in young adults. STUDY DESIGN: This was a cross-sectional study. METHODS: This cross-sectional study included a nationally representative sample of young adults aged 19-29 years (n = 2113). SJL was calculated as the difference in the midpoint of sleep onset and offset time between weekdays and weekends. The dependent variables were engagement in ≥150 min/week of moderate-to-vigorous LTPA and engagement in MSE ≥2 days/week based on guidelines provided by the World Health Organisation. Logistic regression analysis was performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Non-linear relationships were estimated using restricted cubic spline regression. RESULTS: The study population comprised 975 men and 1138 women. Among participants, 4.6% had <0 min, 41.9% had 0-59 min, 25.7% had 60-119 min and 27.7% had ≥120 min SJL. Those with ≥120 min SJL had a reduced likelihood of achieving the recommended level of LTPA (OR: 0.71, 95% CI: 0.52-0.95) and MSE (OR: 0.73, 95% CI: 0.55-0.97). In the non-linear model, an inverse U-shaped association was observed, wherein the highest probability of meeting the recommended level of LTPA and MSE was observed in those with 45 min SJL, decreasing after this threshold. CONCLUSIONS: Individuals with ≥120 min SJL were less likely to engage in the recommended level of both aerobic and anaerobic exercise. Although future studies using a longitudinal design are required to elucidate the causal relationship between SJL and physical activity, the current findings suggest that physical inactivity during leisure time may play an important role in the increased risk of cardiometabolic abnormalities in young adults with SJL.

Effects of military life on changes in body mass index of enlisted men: a cross-sectional study.

BACKGROUND: Obesity is a serious health problem with an incidence that is increasing rapidly. Enlisted men are a distinctive group characterised by 24-hour community-living and are likely to experience changes in body weight as a result of regular diet and exercise during enlistment. METHODS: This study reviewed data from the Second Military Health Survey. Changes in body mass index (BMI) before and during military service were analysed using paired t-test. We calculated OR and 95% CI for factors affecting weight improvement during military service through logistic regression. RESULTS: The mean BMI in the underweight group increased by 5.87 kg/m2 during service, while that in the normal weight group increased by 1.18 kg/m2. In contrast, the mean BMI in the overweight group decreased by 5.47 kg/m2 during service. The OR for an improved BMI in the subjective good health group compared with the subjective poor health group was statistically significant (OR=1.71, 95% CI 1.02 to 2.87). The OR for an improved BMI was significantly higher in the group with three or more times per week of strength training than in the group with one to two times per week of strength training, and was higher among the marines compared with the Army soldiers (OR=1.48, 95% CI 1.03 to 2.12 and OR=2.15, 95% CI 1.07 to 4.32, respectively). CONCLUSIONS: Strength training showed a statistically significant increase in BMI during military service. Furthermore, the BMI of men who were underweight before their service increased, while it decreased among those who were overweight.

Effect of temperature on the breakthrough of a charcoal tube during vinyl chloride monomer sampling.

This study evaluated the effects of temperature on breakthrough of two standard collection media at various concentrations during vinyl chloride monomer (VCM) sampling. The National Institute for Occupational Safety and Health (NIOSH) and Occupational Safety and Health Administration (OSHA) methods were evaluated. To determine whether breakthrough of VCM would occur at the extremes of exposure and temperature that might be encountered in some workplaces, air samples containing 4 ppm (10.24 mg/m3), 8 ppm (20.45 mg/m3), 16 ppm (40.98 mg/m3), and 32 ppm (81.80 mg/m3) of VCM were collected at temperatures of 4, 22, and 40 degrees C. Five liters of air was sampled at the rate of 0.05 L/min for 100 min using the activated charcoal tube recommended by NIOSH. A second tube was added to the sampling train to collect any VCM that might not have been absorbed in the first tube. To collect VCM air samples by the OSHA method, two carbon molecular sieve tubes were connected serially and 3 L of air was sampled at the rate of 0.05 L/min for 60 min. A gas chromatograph with a flame ionization detector and ultra 2 capillary column was used to analyze VCM. Significant breakthrough was found when sampling at higher temperatures with the NIOSH method. No breakthrough was found when samples were collected using the OSHA media at different temperatures and concentrations. Therefore, under hot ambient conditions (>22 degrees C), the possibility of breakthrough should be considered when sampling VCM by the NIOSH method.

Role of skin prick test and serological measurement of specific IgE in the diagnosis of occupational asthma resulting from exposure to vinyl sulphone reactive dyes.

OBJECTIVES: Some patients with occupational asthma resulting from exposure to reactive dyes have skin reactivity to the causative dyes and specific IgE to reactive dyes have been found in these patients. However, the usefulness of skin prick tests (SPTs) and serological measurement of specific IgE in screening, diagnosis, and monitoring the occupational asthma resulting from exposure to reactive dyes have not yet been assessed. In this study, the clinical validation of SPTs and measurement of specific IgE to vinyl sulphone reactive dyes by enzyme linked immunosorbent assay (ELISA) was evaluated. METHODS: 42 Patients with occupational asthma from reactive dyes (true positive group) were enrolled. In these the causative reactive dye was confirmed by bronchial challenge test. 93 Asymptomatic factory workers with negative challenge to the reactive dye (true negative group) and 16 unexposed controls with negative challenge to the reactive dye were also enrolled. Skin prick tests were done with 10 mg/ml reactive dye in 0.4% phenol/0.9% saline. IgE specific to reactive dye conjugated to human serum albumin (HSA) was measured with enzyme linked immunosorbent assays (ELISAs). RESULTS: None of the unexposed controls had a positive response to SPTs. The sensitivity (76.2% v 53.7%), specificity (91.4% v 86.0%), positive predictive value (80.0% v 62.9%), and negative predictive value (89.5% v 80.8%) of SPTs were higher than those of ELISAs. The mean weal size of reaction to reactive dye was weakly correlated with the ELISA optical density of IgE to reactive dye conjugate in patients with occupational asthma from reactive dyes (n=41, r=0.337, p<0.05). In four patients with occupational asthma from reactive dyes and eight control subjects exposed to reactive dye, IgE specific to reactive dye conjugated to HSA was detected with ELISA even though they showed negative skin reactivity. Six patients completely avoided the reactive dye for a mean (SD) 27.8 (10.3) months, IgE specific to reactive dyes decreased in all six patients (p<0.05) during this time. CONCLUSIONS: Both SPTs and detection of IgE specific to reactive dye in serum samples could be valuable for screening, diagnosis, and monitoring occupational asthma resulting from exposure to reactive dyes. These two tests would complement each other.