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Korean J Fam Med > Volume 38(2); 2017 > Article
Lee: Shift Work and Health Problems
Shift work is a reasonably common form of employment and recently, the number of shift workers has increased rapidly. A Korean working condition survey reported that the proportion of employees involved in shift work increased from 7.2% in 2006 to 10.9% in 2010.1,2)
Many diseases and health problems such as sleep disorders, cardiovascular diseases, reproductive issues, depressive mood, and increased mortality have been reported to be linked to shift work.3)
Several studies on shift work problems have been published in the Korean Journal of Family Medicine.4,5,6) Most of the subjects in those studies were hospital employees, and the number of the participants was relatively small.
On the topic of shift work, two studies about health behaviors and the prevalence of metabolic syndrome in Korean shift workers were reported.7,8) Both studies analyzed the Korean National Health and Nutritional Examination Survey (KNHANES) data, which provides national representative samples.
In a cross-sectional study of the Korean adult population, Bae et al.7) found that shift work was associated with negative health behaviors, such as smoking, alcohol consumption, and inadequate sleep, although the degree of association differed based on the participants' sex and age.
In another cross-sectional study by Yu et al.,8) an association between shift work and metabolic syndrome was demonstrated in young adults using data from the 2011–2012 KNHANES database. This study included 3,317 individuals ranging from 20 to 40 years of age. The prevalence of metabolic syndrome was 14.3% and 7.1% among male and female shift workers, respectively. After adjusting for confounding factors, shift work was associated with metabolic syndrome in female workers (odds ratio, 2.53; 95% confidence interval, 1.12 to 5.70). Few studies have evaluated the association between shift work and metabolic syndrome in younger adults, especially using data from the KNHANES database. This study is the first to evaluate the relationship between shift work and metabolic syndrome in young workers.
Interestingly, only female shift workers tended to have more unfavorable health problems and higher prevalence of metabolic syndrome than female day workers in the two studies considered here. They found that only the female shift workers aged ≥50 years were more likely to be current smokers, and partake in high-risk drinking.7) Because the smoking rate and the high-risk drinking rate were higher in all male worker age groups and in the younger age group for female workers, the influence of shift work on smoking and alcohol consumption in this particular group of women was weaker than expected. They also observed a higher proportion of those affected by inadequate sleep in the shift workers of both sexes, and the association between shift work and inadequate sleep was especially evident in men aged 20 to 39 years and in women aged ≥50 years.
Shift work was associated with metabolic syndrome in female workers but not in male workers.8) The authors explained this discrepancy by a high prevalence of menstrual irregularity and high obesity rates in shift workers. A prospective study reported that menstrual cycle irregularity might be a risk factor for metabolic abnormalities that could predispose individuals to the development of cardiovascular disease.9) Another cross-sectional survey reported that night shift work was associated with the development of obesity among night shift-working females.10)
However, as the KNHANES database does not include occupational qualitative data, they were not able to perform a detailed analysis of occupational qualitative data, such as the duration of shift work, intensity of work, and job categories. More prospective studies are needed to evaluate these potentially causal relationships.
Nonetheless, these studies imply the need to implement active strategies to reduce negative health behavior in shift workers to prevent adverse health outcomes.


CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported.


1. Wang JH, Lee G, Song JT, Kwon J, Choi H, Jung-Choi K, et al. The association between shift work and bone mineral density: analysis of 2008-2009 Korean National Health and Nutrition Examination Survey. Korean J Occup Environ Med 2012;24:274–286.
2. 2006 Occupational Safety and Health Research Institute. Korean working condition survey report. Ulsan: Occupational Safety and Health Research Institute; 2006.

3. Rosa RR, Colligan MJ. National Institute for Occupational Safety and Health. Plain language about shiftwork. Cincinnati (OH): National Institute for Occupational Safety and Health; 1997.

4. Choi J, Song YM, Kim S, Park YM, Cho M. A relationship between irritable bowel syndrome and physical activity in women nurses with shift work. Korean J Fam Med 2010;31:529–539.
5. Jung YJ, Sa EJ, Kim MN, Lee DU, Park KH, Sung NJ. Alteration of circadian diurnal rhythms of cardiovascular parameters by night shift work in 3 shift nurses. J Korean Acad Fam Med 2007;28:187–194.

6. Bae JH, Jeong JH. Combined effects of individual background, work shift and job stress on the prevalence of sleep problems in hospital employers. J Korean Acad Fam Med 2003;24:232–244.

7. Bae MJ, Song YM, Shin JY, Choi BY, Keum JH, Lee EA. The association between shift work and health behavior: findings from the Korean National Health and Nutrition Examination Survey. Korean J Fam Med 2017;38:86–92.
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8. Yu KH, Yi YH, Kim YJ, Cho BM, Lee SY, Lee JG, et al. Shift work is associated with metabolic syndrome in young female Korean workers. Korean J Fam Med 2017;38:51–56.
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9. Solomon CG, Hu FB, Dunaif A, Rich-Edwards JE, Stampfer MJ, Willett WC, et al. Menstrual cycle irregularity and risk for future cardiovascular disease. J Clin Endocrinol Metab 2002;87:2013–2017. PMID: 11994334.
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10. Peplonska B, Bukowska A, Sobala W. Association of rotating night shift work with BMI and abdominal obesity among nurses and midwives. PLoS One 2015;10:e0133761PMID: 26196859.
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