Journal List > Korean J Occup Environ Med > v.24(3) > 1125594

Wang, Lee, Song, Kwon, Choi, Jung-Choi, and Lim: The Association between Shift Work and Bone Mineral Density : analysis of 2008-2009 Korean National Health and Nutrition Examination Survey

Abstract

Objectives

The objectives of this study were to explore the association between shift work and the bone mineral density in a representative sample of Korean workers.

Methods

He data from the Fourth Korean National Health and Nutrition Examination Survey (2008-2009) was used. The participants were Korean workers aged 16 to 60 years. Logistic regression analysis was applied to determine the association between shift work and the bone mineral density after controlling for covariates using the SAS version 9.3 package program.

Results

The blood vitamin D level in shift workers was significantly lower than that of day workers in both males and females. In male shift workers, shift work was significantly associated with a decreased bone mineral density in the femoral neck (odds ratio(OR) 1.42, 95% confidence interval(CI)=1.05~1.92) and lumbar spine (OR 1.53, 95% CI=1.09~2.15) compared to day workers. After controlling for covariates, this association was still significant. In the case of female shift workers, shift work was significantly related to a decreased bone mineral density in the total femur (OR 2.84, 95% CI=1.69~4.79) and lumbar spine (OR 1.58, 95% CI=1.12~2.24). After controlling for covariates, this risk was not statistically significant.

Conclusions

The blood vitamin D level of shift workers was significantly lower than that of day workers. In male shift workers, shift work can decrease the bone mineral density in the femoral neck and lumbar spine. Prospective studies with information on the shift work intensity and duration and exposuredata to explain mechanisms will be needed.

Figures and Tables

Fig. 1
Flow diagram of study population.
kjoem-24-274-g001
Table 1
General characteristics of study population
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*column percentage, standard deviation, by Korean Standard Classification of Occupations, 6th version.

§pm14:00~24:00, pm21:00~next day am8:00, work for two and more segments per work day.

Table 2
Results of other related characteristics with bone mineral density in both male and female workers by shift work
kjoem-24-274-i002

*standard deviation.

heavy drinker; drink more than one time per week and six glasses per time in male(more than four glasses in female).

active physical activity(yes) or mild physical activity(yes) or walking exercise(yes).

§geometric mean.

geometric standard deviation.

Table 3
Results of bone mineral density and related laboratory data in both male and female workers by shift work
kjoem-24-274-i003

*standard deviation.

Table 4
Odds ratios(OR) for decreased bone mineral density by T-score in shift workers by sex
kjoem-24-274-i004

*Crude model; day work versus shift work.

Model 1; adjusted with work related variables, such as, job(manual vs non-manual), heavy material handling(yes or no), working time(hours).

Model 2; adjusted with individual factors(weight, smoking, alcohol consumption, exercise, family history of osteoporosis, coffee consumption, sleep hours), socioeconomic status factors(education, income), and hazardous material exposure factors(lead, cadmium).

§odds ratio.

onfidence interval.

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