Ann Occup Environ Med.  2017 ;29(1):25. 10.1186/s40557-017-0187-7.

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

• Jung YS
• Chae CH
• Kim YO
• Son JS
• Kim CW
• Park HO
• Lee JH
• Shin YH
• Kwak HS

• KMID: 2455005
• DOI: http://doi.org/10.1186/s40557-017-0187-7

Abstract

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.

Keyword

Fixed day workers; Serum vitamin D; Sleep quality

MeSH Terms

Alcohol Drinking
Body Mass Index
Depression
Education
Female
Gyeongsangnam-do
Health Personnel*
Humans
Korea*
Life Style
Logistic Models
Male
Marital Status
Sleep Wake Disorders
Smoke
Smoking
Vitamin D Deficiency
Vitamin D*
Vitamins*
Smoke
Vitamin D
Vitamins