The effect of shift work on high sensitivity C-reactive protein level among female workers.

BACKGROUND: This study assessed the association between shift work and high-sensitivity C-reactive protein (hs-CRP) level, a risk factor for cardiovascular disease (CVD), in female workers in electronics manufacturing services (EMS). METHODS: Female EMS workers who received special medical examinations for workers in Gyeongnam, Korea between January 2017 and December 2017 were enrolled in this study. Their age, marital status, education level, alcohol consumption, smoking habit, regular exercise, quality of sleep, work stress, and depression were investigated, and blood tests were conducted. The t- and χ2 tests were conducted to compare the general and biochemical characteristics between daytime and shift worker groups. Age-adjusted partial correlation analysis was performed to examine the linear relationship between hs-CRP level and other risk factors for CVDs. In addition, the difference in hs-CRP levels according to work schedule was analyzed by ANCOVA after adjusting for variables that could affect the hs-CRP level. RESULTS: Although the average hs-CRP levels did not differ significantly between daytime and shift workers (0.92 ± 1.87 and 1.07 ± 2.20 mg/dL, respectively), shift workers tended to show a higher hs-CRP level (p = 0.067). After adjusting for variables that can affect the hs-CRP level, the estimated average hs-CRP level was significantly higher in shift workers (1.325 ± 0.156 mg/dL) than that in daytime workers (0.652 ± 0.350 mg/dL) (p = 0.003). CONCLUSIONS: The results of this study identified a relationship between shift work and hs-CRP level increase in women. Because multiple studies have reported associations between increased hs-CRP and CVD, follow-up of hs-CRP may help early detection of CVD in shift workers.

Comparison of risk-assessment tools for cardio-cerebrovascular diseases (CVD) in male shipyard workers: a cross-sectional study.

BACKGROUND: Periodic revision of assessment tools is essential to ensure risk assessment reliability and validity. Despite the recent revision of the Korea Occupational Safety and Health Agency (KOSHA) 2018, there is no evidence showing that the revision is superior to other cardio-cerebrovascular diseases (CVDs) risk-assessment tools for workplace health management. We conducted a comparative analysis using the Framingham risk score (FRS) as a gold standard to identify the most relevant CVDs risk-assessment tool for workplace health management. METHODS: We included 4,460 shipyard workers who had undergone a workers' health examination during January-December 2016. Risk levels for CVDs were calculated based on the FRS, KOSHA 2013, KOSHA 2017, KOSHA 2018 (2 methods), National Health Screening Program health risk appraisal (NHS HRA) 2017, and NHS HRA 2018. Study participants were categorized into low-risk, moderate-risk, or high-risk groups. Sensitivity, specificity, correlation, and agreement of each risk-assessment tool were calculated compared with the FRS as a gold standard. For statistical analyses, Spearman's rank correlation coefficient and the linearly weighted kappa coefficient were calculated. RESULTS: Sensitivity of the risk assessments was highest in the KOSHA 2018 (health risk appraisal [HRA]). The FRS showed correlation coefficients of 0.354 with the KOSHA 2013, 0.396 with the KOSHA 2017, 0.386 with the KOSHA 2018, 0.505 with the KOSHA 2018 (HRA), 0.288 with the NHS HRA 2017, and 0.622 with the NHS HRA 2018. Kappa values, calculated to examine the agreement in relation to the KOSHA 2013, KOSHA 2017, KOSHA 2018, KOSHA 2018 (HRA), NHS HRA 2017, and NHS HRA 2018 with the FRS, were 0.268, 0.322, 0.352, 0.136, 0.221, and 0.559, respectively. CONCLUSIONS: The NHS HRA 2018 risk calculation method is a useful risk-assessment tool for CVDs, but only when appropriate classification criteria are applied. In order to enhance the risk-group identification capability of the KOSHA guideline, we propose to apply the classification criteria set in this study based on the risk group definition of the 2018 Korean Society of Hypertension guidelines for the management of hypertension instead of the current classification criteria of the KOSHA 2018.

Changes of depression and job stress in workers after merger without downsizing.

BACKGROUND: Since the 1980s, restructuring, which includes downsizing, closures, mergers, and privatization, has expanded worldwide, and various studies have investigated its effect on health. However, previous studies have mainly focused on restructuring accompanied by massive lay-offs, and the effect of a merger on workers' health is still controversial. This study aims to investigate changes in worker depression and job stress after a merger without downsizing, which is unusual in Korea. METHODS: Repeated surveys were done in April 2014, April 2015, and April 2016 involving the participation of 209 subjects. Participants were divided into two groups, which were comprised of blue-collar workers (104) and white-collar workers (105). Sociodemographic characteristics, including age, education level, job tenure, gender, marital status, smoking status, and alcohol consumption, were measured via a survey. To determine the level of depression, the Korean version of the Center for Epidemiologic Studies Depression Scale (CES-D) was employed, and to investigate job stress, the Korean Occupational Stress Scale-Short Form (KOSS-SF) was used. For statistical analyses, Pearson's chi-square test, the Student's t-test, and repeated measure analysis of variance (ANOVA) were performed. RESULTS: The results showed that depression (CES-D, F[2, 400] = 0.466, p = 0.628) was changed but without significance and job stress (KOSS-SF, F[1.899, 379.831] = 3.192, p = 0.045) were significantly different. The between-group difference in the CES-D score between the blue- and white-collar workers by survey administration time was not statistically significant (F = 0.316, p = 0.574). The interaction between the survey time and occupational group was also not statistically significant (F = 0.967, p = 0.381). The between-group difference in the KOSS-SF total score was not statistically significant (F = 1.132, p = 0.289), and the interaction between the survey administration time and occupational group was also not significant (F = 0.817, p = 0.437). In the job stress subgroup analyses Job insecurity and Lack of reward showed a significant difference by survey administration time. CONCLUSION: This study showed that a merger without massive downsizing can cause negative health effects such as an changes in depression and increase in job stress. To improve the health of workers, both the immediate negative effects on health, and the long-term effects or their resolution over time should be considered prior to the merger.

The relationship between serum vitamin D levels and sleep quality in fixed day indoor field workers in the electronics manufacturing industry in Korea.

BACKGROUND: Although recent studies have investigated the influence of vitamin D on sleep patterns, there is a lack of research on the relationship between vitamin D and sleep patterns in Korean workers. This study focused on the relationship between serum vitamin D levels and sleep in fixed day indoor field workers in the electronics manufacturing industry in Korea. METHODS: The 1472 subjects who were included in this study were selected from fixed day workers in the electronics manufacturing industry who had received a worker's special health examination at a hospital in Changwon, South Gyeongsang Province between January 2015 and December 2015. Nighttime workers and those who showed symptoms of depression were excluded from this study. The sociodemographic and lifestyle variables of the participants were investigated, including age, sex, marital status, level of education, body mass index, smoking habits, alcohol consumption habits, and regular exercise. Work-related factors were evaluated, such as employee tenure and occupational stress. Serum 25-hydroxyvitamin D was measured as an indicator of vitamin D levels, and quality of sleep was evaluated using the Pittsburgh Sleep Quality Index (PSQI) translated into Korean. RESULTS: The subjects had a mean serum vitamin D level of 13.70 ± 5.93 ng/mL. Vitamin D deficiency, defined as a serum vitamin D level of <10 ng/mL, was found in 24.8% of males and significantly more frequently in females (47.6%). Poor sleep quality was reported by 19.8% of participants with serum vitamin D levels ≥10 ng/mL and by 21.7% of those with serum vitamin D levels <10 ng/mL, which was a significant difference (P = .007). Multiple logistic regression analysis adjusting for significant variables found that poor sleep quality was more likely in those with vitamin D deficiency than those with higher serum vitamin D levels (odds ratio = 1.36; 95% CI, 1.01-1.82). A comparison of serum vitamin D levels and PSQI components showed that the mean scores for subjective sleep quality, sleep latency, and sleep duration were significantly higher in the vitamin D-deficient participants, indicating that the vitamin D-deficient participants had poorer sleep quality. CONCLUSIONS: This study investigated serum vitamin D levels in fixed day indoor field workers in the manufacturing industry in Korea and analyzed the relationship of vitamin D deficiency with sleep quality. A significant correlation was found between serum vitamin D deficiency and poor sleep quality. Based on the results of this study, sleep disorder management for workers can be improved by providing regular examinations checking their serum vitamin D levels and supplying vitamin D to workers with serum vitamin D deficiency to enhance their quality of sleep.

Erratum to: The relationship between quality of sleep and night shift rotation interval.

[This corrects the article DOI: 10.1186/s40557-015-0084-x.].

Association between serum vitamin D and depressive symptoms among female workers in the manufacturing industry.

BACKGROUND: Vitamin D has been known to maintain the body's balance of calcium and phosphorus as well as skeletal health. There has been increasing emphasis on the importance of vitamin D as recent studies have been reporting the specific functions of vitamin D in the cerebral nervous system and the association between the level of serum vitamin D and depressive symptoms. However, there is currently a paucity of research investigating the association between serum vitamin D and depressive symptoms in Korean subjects. Consequently, this study has aimed to determine the level of serum vitamin D and explore the association between serum vitamin D and depressive symptoms in Korean female workers. METHOD: A medical examination, questionnaire, anthropometric measurements, and a blood test were conducted between February 3 and March 7, 2014 in 1054 subjects among female workers in the manufacturing industry who underwent physical examinations in a university hospital. From this data, we identified the level of serum vitamin D and investigated the association between serum vitamin D deficiency and depressive symptoms. RESULTS: The average serum vitamin D level of the 1054 subjects was 9.07 ± 3.25 ng/mL, and the number of subjects in the serum vitamin D deficiency group with less than 10 ng/mL was 721 (68.4 %). The odds ratio of the depressive symptom group with a CES-D score of 16 or above being in the deficiency group with a serum vitamin D level less than 10 ng/mL was found to be 1.55 (95 % CI = 1.15-2.07). CONCLUSION: 68.4 % of female workers in the manufacturing industry were in the deficiency group with serum vitamin D levels less than 10 ng/mL. Additionally, we identified an association between serum vitamin D deficiency and depressive symptoms. In the future, if serum vitamin D deficiency is checked regularly in workers, we expect to achieve better outcomes in managing their depressive symptoms.

The relationship between quality of sleep and night shift rotation interval.

BACKGROUND: Shift work is closely related with workers' health. In particular, sleep is thought to be affected by shift work. In addition, shift work has been reported to be associated with the type or direction of shift rotation, number of consecutive night shifts, and number of off-duty days. We aimed to analyze the association between the night shift rotation interval and the quality of sleep reported by Korean female shift workers. METHODS: In total, 2,818 female shift workers from the manufacturing industry who received an employee physical examination at a single university hospital from January to August in 2014 were included. Subjects were classified into three groups (A, B, and C) by their night shift rotation interval. The quality of sleep was measured using the Korean version of the Pittsburgh Sleep Quality Index (PSQI). Descriptive analysis, univariate logistic regression, and multivariate logistic regression were performed. RESULTS: With group A as the reference, the odds ratio (OR) for having a seriously low quality of sleep was 1.456 (95% CI 1.171-1.811) and 2.348 (95% CI 1.852-2.977) for groups B and C, respectively. Thus, group C with the shortest night shift rotation interval was most likely to have a low quality of sleep. After adjustment for age, obesity, smoking status, alcohol consumption, exercise, being allowed to sleep during night shifts, work experience, and shift work experience, groups B and C had ORs of 1.419 (95% CI 1.134-1.777) and 2.238 (95% CI 1.737-2.882), respectively, compared to group A. CONCLUSION: Our data suggest that a shorter night shift rotation interval does not provide enough recovery time to adjust the circadian rhythm, resulting in a low quality of sleep. Because shift work is influenced by many different factors, future studies should aim to determine the most optimal shift work model and collect accurate, prospective data.