Distribution of volatile organic compounds by distance from industrial complexes and potential health impact on the residents.

Volatile organic compounds (VOCs) are the air pollutants emitted from the petrochemical industry known to pose adverse health effects on workers. The database based on the third phase of The Environmental Health Study in the Korean National Industrial Complexes (EHSNIC) in Ulsan conducted from 2018 to 2021 was used. Subjects were divided into the exposed and control group according to the estimated pollution level and distances from the industrial complexes. Ambient benzene, ethylbenzene, and xylene were significantly higher in the exposed group compared to the controls, as well as their metabolites. Risk of chronic disease and atopic dermatitis was higher in the exposed group which was supported by higher serum inflammatory markers and high hazard index of the exposed region. These results can draw attention to people engaged with environmental plans and used as primary data when making policies to reduce pollutant levels around industrial complexes.

Effect of Noise on Sleep and Autonomic Activity in Children according to Source.

BACKGROUND: Noise has been a major issue in children due to its effect on emotional symptoms and sleep problems. The present study investigated the effect of noise on sleep and autonomic activity in children according to three variables, namely, road traffic noise, aircraft noise, and noise sensitivity (NS). METHODS: The study is epidemiological in nature. A total of 474 subjects of four elementary schools were evaluated in conjunction with the 2014 noise map data gathered from two metropolitan regions, Seoul and Ulsan, in South Korea. Each subject completed the children's sleep habits questionnaire, and heart rate variability (HRV) was recorded. Analysis of covariance was performed using monthly income as a covariate. RESULTS: Aircraft noise was associated with night waking (P = 0.047), whereas no significant association was observed between sleep and road traffic noise. After stratifying by NS, no significant results were obtained for road traffic noise. However, high levels of aircraft noise in the high-NS group were associated with high degrees of bedtime resistance (P = 0.049). In terms of HRV, no significant difference was observed in the results between groups. CONCLUSION: Road traffic noise did not significantly alter sleep or autonomic activity in children, whereas aircraft noise exerted a negative effect on sleep. The findings suggest that the impact of noise on sleep in children varies depending on noise sources.

Environmental and Body Concentrations of Heavy Metals at Sites Near and Distant from Industrial Complexes in Ulsan, Korea.

BACKGROUND: Industrial pollution may affect the heavy metal body burden of people living near industrial complexes. We determined the average concentrations of atmospheric heavy metals in areas close to and distant from industrial complexes in Korea, and the body concentrations of these heavy metals in residents living near and distant from these facilities. METHODS: The atmospheric data of heavy metals (lead and cadmium) were from the Regional Air Monitoring Network in Ulsan. We recruited 1,148 participants, 872 who lived near an industrial complex ("exposed" group) and 276 who lived distant from industrial complexes ("non-exposed" group), and measured their concentrations of blood lead, urinary cadmium, and urinary total mercury. RESULTS: The results showed that atmospheric and human concentrations of heavy metals were higher in areas near industrial complexes. In addition, residents living near industrial complexes had higher individual and combined concentrations (cadmium + lead + mercury) of heavy metals. CONCLUSION: We conclude that residents living near industrial complexes are exposed to high concentrations of heavy metals, and should be carefully monitored.

Negative impact of noise and noise sensitivity on mental health in childhood.

INTRODUCTION: Noise and noise sensitivity have negative effects on mental health and are not well-studied in children and adolescents. In this study, we investigated these effects in the aforementioned population with respect to sociodemographic variables and environmental factors. MATERIALS AND METHODS: In this population-based study conducted in two large cities in South Korea, 918 elementary and middle-school students were included. After direct measurements at the selected sites, a noise map was created using an interpolation method. The road traffic noise of the participants' residential areas was calculated based on this noise map. Noise sensitivity was assessed on an 11-point Likert scale. Using multivariate logistic regression, we investigated the relationship among noise, noise sensitivity, and the Child Behavior Checklist. Further analyses were performed subdividing the data according to household income levels. RESULTS: Noise sensitivity was significantly associated with internalizing, externalizing, and total behavioral problems. Noise was positively associated with total behavioral problems. In the low-income group, the degree of association with problem behaviors was higher, whereas the relationship between noise sensitivity and externalization problems disappeared in the high-income group. CONCLUSION: Noise and noise sensitivity are negatively associated with the mental health of children and adolescents, particularly in low-income groups. The findings of this study suggest that noise sensitivity and socioeconomic status should be considered in coping with negative effects of noise in children and adolescents.

Noise sensitivity, rather than noise level, predicts the non-auditory effects of noise in community samples: a population-based survey.

BACKGROUND: Excessive noise affects human health and interferes with daily activities. Although environmental noise may not directly cause mental illness, it may accelerate and intensify the development of latent mental disorders. Noise sensitivity (NS) is considered a moderator of non-auditory noise effects. In the present study, we aimed to assess whether NS is associated with non-auditory effects. METHODS: We recruited a community sample of 1836 residents residing in Ulsan and Seoul, South Korea. From July to November 2015, participants were interviewed regarding their demographic characteristics, socioeconomic status, medical history, and NS. The non-auditory effects of noise were assessed using the Center of Epidemiologic Studies Depression, Insomnia Severity index, State Trait Anxiety Inventory state subscale, and Stress Response Inventory-Modified Form. Individual noise levels were recorded from noise maps. A three-model multivariate logistic regression analysis was performed to identify factors that might affect psychiatric illnesses. RESULTS: Participants ranged in age from 19 to 91 years (mean: 47.0 ± 16.1 years), and 37.9% (n = 696) were male. Participants with high NS were more likely to have been diagnosed with diabetes and hyperlipidemia and to use psychiatric medication. The multivariable analysis indicated that even after adjusting for noise-related variables, sociodemographic factors, medical illness, and duration of residence, subjects in the high NS group were more than 2 times more likely to experience depression and insomnia and 1.9 times more likely to have anxiety, compared with those in the low NS group. Noise exposure level was not identified as an explanatory value. CONCLUSIONS: NS increases the susceptibility and hence moderates there actions of individuals to noise. NS, rather than noise itself, is associated with an elevated susceptibility to non-auditory effects.

Estimating the severity distribution of disease in South Korea using EQ-5D-3L: a cross-sectional study.

BACKGROUND: There is a paucity of data on the distribution of disease severity. In this study, we estimated disease severity distributions in South Korea using two EQ-5D-3L population surveys. METHODS: A total of 110 health states for 35 diseases with 2-5 severity levels (e.g., mild, moderate, severe) were included in this study. A general population of 360 participants from the areas surrounding Seoul and Gyunggi evaluated these health states using EQ-5D-3L via face-to-face interviews and a paper questionnaire. The EQ-5D indices were used to measure the severity levels of health states and used as the cutoff points for the disease severity distributions. Finally, these cutoff points were applied to disease prevalence data with EQ-5D-3L, which were obtained from the Korean National Health and Nutrition Examination Surveys (KNHNES) and Korean Community Health Survey, in order to estimate the disease severity distributions. RESULTS: The severity distributions of 8 diseases were estimated, including asthma, angina, stroke, chronic obstructive pulmonary disease, major depressive disorder, musculoskeletal problems in the legs, anemia, and allergic rhinitis and conjunctivitis. For example, the EQ-5D indices for chronic obstructive pulmonary disease severity were 0.929, 0.742, and 0.620, and the cut-off points were 0.835 (between mild and moderate) and 0.681 (between moderate and severe). Using these cutoff points, the distributions of chronic obstructive pulmonary disease severity were 66.5 % (mild), 23.3 % (moderate), and 10.1 % (severe) according to KNHNES. CONCLUSIONS: The estimated severity distributions in this study can be used as a valid calculation of the disease burden in the general population.

Oxidative stress in schoolchildren with allergic rhinitis: propensity score matching case-control study.

BACKGROUND: Oxidative stress is defined as an imbalance between the level of reactive oxygen species and antioxidant mechanisms. Compared with asthma, the role of oxidative stress in allergic rhinitis (AR) has received little attention. OBJECTIVE: To investigate the association between overall systemic oxidative stress and AR. METHODS: We used a propensity score matching case-control study and selected 90 children who had experienced AR in the previous year. This AR group was then matched with 90 healthy children who comprised the control group. Propensity score matching, a statistical matching technique that accounts for the conditional probability of receiving an exposure given a vector of measured covariates, is used to reduce selection bias and potential confounders in observational study. Serum total antioxidant status (TAS) and total oxidant status (TOS) levels were determined using a commercially available assay kit. Medical records and personal information were also reviewed. RESULTS: No statistically significant differences were found between patients with regard to age, sex, height, weight, educational level of parent, monthly household income, or distance of home from a main road. The mean TAS and TOS levels in the patient group were significantly higher than those of the control group (P = .03 and .048, respectively). The oxidative stress index, which is defined as the ratio of TOS to TAS, also increased in the AR group with statistical propensity (P = .08). In a multivariate logistic analysis, only TAS and TOS levels were significantly associated with increased risk of allergic rhinitis. CONCLUSION: Patients with AR have systemically elevated oxidative stress and systemically elevated TAS levels.

Associations between blood mercury levels and subclinical changes in liver enzymes among South Korean general adults: analysis of 2008-2012 Korean national health and nutrition examination survey data.

INTRODUCTION: We herein used data from the Korean National Health and Nutritional Examination Survey (KNHANES) 2008-2012 to examine the associations between blood mercury levels and subclinical changes of liver function in a representative sample of the adult Korean population. METHODS: This study was based on data obtained from KNHANES, in which a rolling sampling design was used to perform a complex, stratified, multistage probability cluster survey of a representative sample of the non-institutionalized civilian population in South Korea. The associations between subclinical hepatic changes and blood mercury levels were assessed after adjustment for various demographic and lifestyle factors. RESULTS: Multivariate linear regression analyses revealed that each doubling of blood mercury increased serum aspartate transaminase (AST) by 0.676U/L and serum alanine transaminase (ALT) by 1.067U/L. The mean differences (95% CI) in serum AST and ALT between the lowest and highest quartiles were statistically significant at 1.249 (0.263-2.235)U/L and 2.248 (0.648-3.848), respectively. Logistic regression analysis showed that the odd ratios for having serum AST and ALT levels above the median were statistically significant in both the models according to the increase of blood mercury. The risks of having serum AST and ALT levels higher than the median among subjects in 4th quartile of blood mercury were 1.524 and 1.947, respectively. DISCUSSION: The present findings show that subclinical changes of liver function are associated with blood mercury levels. This is the first study to show an association between blood mercury levels and mild liver dysfunction, as a possible proxy measure of nonalcoholic fatty liver disease (NAFLD), in Asian population.

Iron deficiency increases blood lead levels in boys and pre-menarche girls surveyed in KNHANES 2010-2011.

INTRODUCTION: We present data from the Korean National Health and Nutritional Examination Survey (KNHANES) 2010-11 on the distribution of blood lead levels, and examine their association with iron deficiency in a representative sample of the adolescent Korean population. METHODS: This study was based on data obtained from KNHANES, in which a rolling sampling design was used to perform a complex, stratified, multistage probability cluster survey of a representative sample of the non-institutionalized civilian population in South Korea. Serum ferritin was categorized into three levels: low (serum ferritin <15.0µg/L), low normal (serum ferritin 15.0-30.0µg/L for girls and 15.0-50.0 for boys), and normal (serum ferritin ≥30.0µg/L for girls and ≥50.0 for boys), and its association with blood lead levels was assessed after adjustment for various demographic and lifestyle factors. RESULTS: The geometric mean (GM) of blood lead in the low serum ferritin group was significantly higher than that in the normal group among boys but not girls. After controlling for covariates, multiple regression analysis showed that blood lead was inversely correlated with serum ferritin levels in boys and pre-menarche girls only. DISCUSSION: The present study shows that iron deficiency increases blood lead levels in a representative sample of the male and pre-menarche female adolescent population, as evaluated in KNHANES. The confounding effect of estrogen on blood lead levels should be considered.

Normative data for neuromuscular assessment of the hand-arm vibration syndrome and its retrospective applications in Korean male workers.

PURPOSE: The purpose of this study was to describe normative data for the neuromuscular assessments of the hand-arm vibration syndrome (HAVS) in Korean. METHODS: Data for the vibrotactile perception threshold (VPT) at three frequencies (31.5, 125, and 250 Hz), the hand grip strength (HGS), the finger pinch strength (FPS), the finger tapping test, and the Purdue pegboard tests were collected from 120 male office workers aged 30-59 years with no prior history of regular use of handheld vibrating tools. The collected data were compared with the results of a similar study of shipbuilding workers in order to investigate the diagnostic utility of clinical test for HAVS. RESULTS: The mean VPT values indicate that no significant differences were observed between the dominant and non-dominant hands or between the index and little fingers. The age group of 30s was highly sensitive to vibration input with a peak in sensitivity at 125 Hz among all age groups. In neuromuscular performance, dominant hands are usually more accurate, dexterous, and functionally quicker than non-dominant hands. The index finger was superior to the little finger in the finger tapping counts (p < 0.05). Also, FPS was greater in the index finger than in the middle finger (p < 0.05). The HGS of dominant hands was significantly stronger than that of non-dominant hands (p < 0.05). When the normative data were compared with the data of shipyard workers exposed to vibration, there were statistically significant differences in VPT and neuromuscular functions. CONCLUSIONS: The current data can be used to evaluate HAVS in Korean male workers. Age is an important factor for VPT.

Association between sleep quality and type of shift work in Korean firefighters.

Background: Shift work that interferes with normal sleep patterns, is known to be a cause of sleep disturbance and has been studied through various occupational groups. However, it is not known which shift type is better for sleep health. Methods: This study included 568 firefighters. Sleep quality was evaluated using Pittsburgh Sleep Quality Index. Sleep quality was categorized into 2 groups; good quality (≤ 5 points) and poor quality (≥ 6 points). Demographic variables, depression, anxiety, type of shift, and job were collected by self-reported questionnaires. The χ2 test, t-test, and multiple logistic regression analysis were used to evaluate the effect of shift type on the sleep quality of firefighters. Results: Three hundred thirty-seven firefighters (59.3%) have poor sleep quality. Compared to day workers, the odds ratios (ORs) of poor sleep quality were 2.169 (95% confidence interval: 1.137-4.134) in 6-day cycle, 2.161 (1.150-4.062) in 9-day cycle, 1.805 (1.087-2.997) in 21-day cycle, and 1.485 (0.718-3.069) in 3-day cycle. The ORs of poor sleep quality were 1.697(1.021-2.823) in fire suppression and 2.325 (1.213-4.455) in emergency medical service compared to administration. Conclusions: All shift work type except for the 3-day cycle was associated with poor sleep quality compared to day work.

Nickel dust-induced occupational contact dermatitis by welding and grinding work in shipyard workers: a report of nine cases.

Background: Occupational skin diseases are skin conditions that occur or worsen in relation to work and known to be the second most common type of occupational disease affecting individuals in the United States. In Korea, epidemiological reports related to occupational skin diseases are rare. But, no cases of occupational contact dermatitis caused by welding and grinding work have been reported previously. Case presentation: Nine male workers working in the production department for liquefied natural gas (LNG) ships in Ulsan complained of erythematous papules/patches and itching in various areas of the body after welding and grinding work. The work environment monitoring report revealed that the amount of nickel dust exceeded the time weighted average (TWA) and poor local ventilation status. Based on the symptoms and the overall results of surveys, several tests, and work environment monitoring report, the 2 workers who had positive patch-test reactions to nickel were diagnosed with nickel dust-induced allergic contact dermatitis. The other 7 workers were diagnosed that there was a high probability that they had nickel dust-induced irritant contact dermatitis. The 2 workers who had nickel dust-induced allergic contact dermatitis were recommended to switch their jobs. Conclusions: Nickel is one of the most common cause of allergic contact dermatitis. In this case, the dust was assumed to be created by welding work with a high nickel content new welding rod and subsequent grinding work, and the concentration of this dust exceeded the time weighted average. Thus, it is thought that the nickel dust may have caused contact dermatitis through continuous contact with the workers' exposed skin in a poorly ventilated space. Currently, several domestic shipbuilding companies are manufacturing LNG tankers using a new construction method. Consequently, it is highly likely that similar cases will occur in the future, which makes this case report meaningful.

The association between direct supervisor's behavior and employee presenteeism in Korean wage workers: findings from the fifth Korean Working Condition Survey.

BACKGROUND: Presenteeism is a phenomenon in which employees go to work, but physical or mental health problems make it impossible for them to properly demonstrate their abilities, and productivity decreases accordingly. Recent studies have considered the behavior of direct supervisors to be an important factor in the pathogenesis of various health-related outcomes. This study aimed to investigate the association between the direct supervisor's behaviors and presenteeism among wage workers in South Korea. METHODS: A total of 25,798 participants from the fifth Korean Working Condition Survey conducted in 2017 were included in the analysis. The behaviors of direct supervisor were assessed by 6 questionnaire items. In this study, the distribution of the scores was categorized into 4 categories (very good, good, bad, and very bad). To assess presenteeism, the corresponding questionnaire item was used. χ2 tests and multiple logistic regression analyses adjusted for general, occupational, and psychosocial factors were performed to determine the association between the behaviors of direct supervisor and presenteeism. RESULTS: Direct supervisor's behavior were significantly associated with presenteeism. The adjusted odds ratios (aORs) of presenteeism in the good, bad, and very bad groups were 1.297 (95% confidence interval [CI]: 1.153-1.458), 1.191 (95% CI: 0.941-1.507), and 1.604 (95% CI: 1.184-2.175), compared with the very good group. Associations between presenteeism and the behaviors of direct supervisor were significant in male workers, but not in female workers. For male workers, the aORs of presenteeism in the good, bad, very bad groups were 1.661 (95% CI: 1.425-1.936), 1.445 (95% CI: 1.053-1.982), 2.340 (95% CI: 1.569-3.491), respectively. CONCLUSIONS: This study suggests that the behavior of a direct supervisor can influence the occurrence of presenteeism, particularly in men. The proper management of senior employee's behaviors is necessary to reduce the risk of presenteeism in the workplace.

Allergic rhinitis is associated with atmospheric SO2: Follow-up study of children from elementary schools in Ulsan, Korea.

OBJECTIVES: The purpose of this study was to examine the association of allergic rhinitis with air pollutant concentrations using the follow-up data of elementary school children in Ulsan, Korea. METHODS: All students of four elementary schools in Ulsan, South Korea were surveyed at two-year intervals. The survey used data collected five times, over a nine-year period from June 2009 to April 2018. The questionnaire used in the survey was a modified version of the ISAAC (International society of asthma and allergy of children) questionnaire. A skin prick test (SPT) was performed with 24 standard antigens. To estimate the levels of exposure to outdoor air pollution, the concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), and particulate matter 10 µm or less in diameter (PM10) were used. As a dependent variable, a history of allergic rhinitis diagnosed by a doctor during the last 1-year was considered. Logistic regression analysis was used to select variables suitable for the statistical model. The selected variables were then used to assess their association with the dependent variable using the generalized estimation equation. RESULTS: Among environmental factors, SO2 was associated with a high risk and PM10 was associated with a low risk of allergic rhinitis. The risk of allergic rhinitis from living in a house built within the last year was high, and the risk from living in a multi-family house or apartment was higher than that from living in a segregated house. History of allergic diseases in the family was a high-risk factor for allergic rhinitis. There was a relationship between a history of bronchiolitis at less than 2 years of age and a high risk of allergic rhinitis. Boys were at a higher risk than girls. CONCLUSION: From the follow-up data of elementary school students in Ulsan, Korea, the concentration of SO2, which is an indicator of the degree of industrialization, was related to the prevalence of allergic rhinitis. Among all the risk factors, history of allergic disease in the parents was the most important factor, and the study reconfirmed the results of the previous studies.

Clinical Importance of Work-Exacerbated Asthma: Findings From a Prospective Asthma Cohort in a Highly Industrialized City in Korea.

PURPOSE: Work-related asthma (WRA) occupies about 10%-30% of all asthma cases. Among 2 subtypes of WRA (occupational asthma [OA] and work-exacerbated asthma [WEA]), the rate of WEA has been reported to increase recently. WRA is described as having worse characteristics than non-WRA (NWRA), while WEA is known to show similar severity to OA in terms of symptoms and exacerbations. However, these data were mainly based on indirect surveys. Ulsan is a highly industrialized city in Korea; therefore, it is estimated to have a high incidence of WRA. This study aimed to identify the characteristics of WRA in the city. METHODS: This was a prospective asthma cohort study of individuals diagnosed with asthma and treated at Ulsan University Hospital between Jan 2015 and Dec 2016. Baseline characteristics and work-related inquiry (9 questionnaires) were investigated at enrollment. Various severity indices and job change were then investigated for the longitudinal analysis at 12 months after enrollment. RESULTS: In total, 217 asthma patients completed the study. WRA accounted for 17% (36/217), with an equal number of WEA and OA (18 patients each). Before the work-related survey, only 33% (n = 12) of WRA patients (22% [4/18] of WEA and 44% [8/18] of OA) were diagnosed with WRA by the attending physicians. Compared to the NWRA group and the OA subgroup, the WEA subgroup had more outpatient visits, more oral corticosteroids prescriptions, and trends of low asthma control test scores and severe asthma. The rate of job change was markedly lower in the WEA subgroup than in the OA subgroup (20% vs. 5%). CONCLUSIONS: The overall prevalence of WRA (17%) was similar to those of previous studies, but the share of WEA was high (50% of WRA). WEA was more severe than OA or NWRA. The possible reason for this severity is ongoing workplace exposure.

Association between shift work and biological factors including FGF-23, klotho, and serum 25-(OH) vitamin D3 among Korean firefighters: a cross-sectional study.

STUDY OBJECTIVES: Shift work is known to be detrimental to an individual's health as it disrupts the circadian rhythm and is a risk factor for cancer. It has been reported that elevated fibroblast growth factor (FGF)-23, increased serum soluble α-klotho, and decreased vitamin D3 are associated with cancer progression. We studied the relationship between shift work and the levels of FGF-23, α-klotho, and vitamin D3 amongst firefighters, as they work in long shifts outside the traditional daytime schedule. METHODS: The study consisted of 450 participants who were firefighters. We measured FGF-23, α-klotho, and vitamin D3 levels in their blood and a set of questionnaires were given to the participants to evaluate their health habits. After determining and adjusting for potential confounding factors, we compared the levels of FGF-23, α-klotho, and serum vitamin D3 by job and shift types. RESULTS: FGF-23 and α-klotho levels were significantly higher in shift workers than traditional day workers, and in 3-day cycle shift workers than workers with another shift schedule. When the levels of these substances were compared based on different types of jobs, firefighters had a lower level of vitamin D3. We conclude that shift work is positively correlated with the levels of FGF-23 and α-klotho. CONCLUSIONS: Levels of FGF-23 and α-klotho were linked to shift work and job types. Although vitamin levels did not differ by shift types, vitamin D3 levels were lower in firefighters. These findings suggest that high levels of FGF-23 and α-klotho are potential risk factors for cancer among firefighters.

Comparison of Cortisol level by Shift Cycle in Korean Firefighters.

(1) Study Objectives: By investigating the change of cortisol levels during shift cycles among professional firefighters in Korea, this study aims to evaluate the difference between individuals' stress response and the recovery of their circadian rhythm after working night shifts. (2) Methods: A total of 325 shift firefighters, who were working in 3, 6, 9, or 21 day cycles, participated in the study. Their urinary and serum cortisol levels were measured during the day (09-18), during the night (18-09), and every 24 h (09-09) per shift cycle, and adjustments were made for confounding factors. (3) Results: Serum cortisol levels were significantly increased after working during the night or for 24 h compared with that of working throughout the day. However, whether working night or 24 h shifts, the serum cortisol levels were undoubtedly different based on the 3, 6, 9, or 21 day cycles. In all shift cycles, the urinary cortisol level decreased during the night or throughout the 24 h shifts compared with sleeping during this time, but this was considered to be significantly applicable only to those working in 21 day cycles. Additionally, in serial measurements, the recovery of urinary cortisol secretion after a night or 24 h shift was successful for individuals working in 9 day cycles, but the recovery was delayed for those working in 6 or 21 day cycles. (4) Conclusions: After analyzing the urine cortisol levels, the study indicates that only subjects working in 9 day cycles fully recovered their circadian rhythm while those working in 6 day or 21 day cycles did not completely recover. Therefore, it is important to recognize how stressful night shifts can be, and it is crucial to enhance firefighters' current shift cycles in order to allow sufficient recovery of their circadian rhythm as well as the prevention of disrupting their circadian rhythm after working at night. Further research is necessary to take into account the amount of work load, the challenges of being sleep deprived, and the individual's capacity to overcome sleepiness.

Association between Shift Work and Neurocognitive Function among Firefighters in South Korea: A Prospective Before-After Study.

Background: Recent research indicates that shift work is associated with neurocognitive function. However, studies that examine the association between shift work and neurocognitive function in firefighters have not yet been performed. We examined the effect of shift work on neurocognitive function in firefighters by measuring and comparing neurocognitive function before and after night shift. Methods: 352 firefighters from eight fire stations in South Korea were included in this study. We performed neurocognitive function test using central nervous system vital signs (CNSVS) during daytime work and on the next day after night work. We performed paired t-tests to assess differences between neurocognitive function before and after night work. We also compared neurocognitive function in insomnia and depression. We used a general linear model to analyze the associations between shiftwork schedule and the changes in neurocognitive function. Results: The neurocognitive function significantly decreased in six domains (composite memory, verbal memory, visual memory, complex attention, psychomotor speed, and motor speed) as did the neurocognitive index on the next day after night work compared with during day work. These decreased domains were the same following night work regardless of the type of shift work. Conclusion: Night work in firefighters may cause neurocognitive decline.

The Prevalence and Incidence of Insomnia in Korea during 2005 to 2013.

OBJECTIVE: The aim of this study was to estimate the progress of insomnia prevalence and incidence over the past several years. Also, this study compared survival rates between individuals with and without insomnia. METHODS: The National Health Insurance Service-National Sample Cohort (NHIS-NSC) from 2002-2013 was used for this study. Prevalent cases of insomnia were defined using ICD-10 codes F51.0 or G47.0, or a prescription of sedatives. Cox's proportional hazard analysis was conducted to compare survival rates between insomnia patients and people without insomnia. RESULTS: In 2013, there were 46,167 (5.78%) insomnia patients over 20 years old in this cohort. Insomnia was more common among women and the elderly. Annual incidence over the past several years remained steady but the prevalence increased. The survival of insomnia patients was lower than that of people without insomnia, and the hazard ratio for overall mortality was 1.702 (p<0.001). CONCLUSION: This large-scale population-based cohort study provided current epidemiologic indicators of insomnia in the Korean general population.

Sleep Assessment During Shift Work in Korean Firefighters: A Cross-Sectional Study.

BACKGROUND: This cross-sectional study assessed the sleep quality using the ActiGraph and investigated the relationship between the parameters of sleep assessment and the type of shift work in Korean firefighters. METHODS: The participants were 359 firefighters: 65 day workers (control group) and 294 shift workers (shift work group: 77 firefighters with 3-day shift, 72 firefighters with 6-day shift, 65 firefighters with 9-day shift, and 80 firefighters with 21-day shift). Sleep assessments were performed using the ActiGraph (wGT3X-BT) for 24 hours during day shift (control and shift work group) and night shift and rest day (shift work group). The participants recorded bed time and sleep hours during the measurement period. RESULTS: Sleep efficiency, total sleep time, and percentage of wake after sleep onset during night work were lower in the shift work group than control group (p < 0.05). Sleep efficiency decreased in night shift and increased in rest day, whereas wake after sleep onset increased in night shift and decreased in rest day (p < 0.05). Among shift work groups, sleep efficiency of 6-day shift was higher in day shift, and sleep efficiency of 21-day shift was lower in night shift than other shift groups (p < 0.05). CONCLUSION: We found that the sleep quality in night shift of the shift work group was poorer than the control group. As to the type of shift work, sleep quality was good in 6-day shift and poor in 21-day shift. Thus, fast rotating shift such as 6-day shift may be recommended to improve the sleep quality of the firefighters.