Low Bone Mineral Density in Rotating-Shift Workers

doi:10.1016/j.jocd.2010.07.004

Journal of Clinical Densitometry

Volume 13, Issue 4, October 2010, Pages 467-469

https://doi.org/10.1016/j.jocd.2010.07.004 Get rights and content

Abstract

Shift workers have been reported to have an increased bone resorption. However, no existing evidence indicates lower bone mineral density (BMD) in this group. The objective of this study was to test the hypothesis that a rotating-shift work schedule is associated with low BMD and osteoporosis. We evaluated 70 postmenopausal nurses from the Naval Hospital in Concepcion, Chile. The participants were categorized according to the type of work schedule: 39 had a rotating shift and 31 were daytime workers. Medical history, a health examination, a questionnaire on health-related behaviors and biochemical determinations, and BMD examination were obtained for all participants. When comparing the 2 groups, the rotating-shift workers had lower BMD in the lumbar spine (L1–L4: 0.957 ± 0.15 vs 1.104 ± 0.13; p < 0.05) and lower bone density in both femoral neck bones (right: 0.936 ± 0.17 vs 1.06 ± 0.12; p < 0.05 and left: 0.956 ± 0.19 vs 1.05 ± 0.12; p < 0.05). Additionally, the T-scores for 10 (25.6%) of the rotating-shift workers indicated osteoporosis at lumbar spine (T-score > −2.5). No evidence of osteoporosis was found for daytime workers. When comparing the 2 groups, the rotating-shift workers had a higher prevalence of osteopenia (T-score = −1.0 to −2.5) than the daytime workers: 46.2% vs 35.5%, respectively. We found significant evidence that rotating-shift workers have lower BMD in the trabecular and cortical bones, thus suggesting that this type of work may be a risk factor for osteoporosis. Because this is the first time that this osteoporosis risk factor has been reported, the association needs to be replicated and confirmed in other settings.

Introduction

Although osteoporosis and subsequent increased fracture risk occur primarily in older persons, a predisposition for osteoporosis is partially established during adulthood.

The number of women in the workforce has grown over the past 20 yr and continues to expand. Many of the women workers in industrialized countries work in rotating shifts 1, 2.

Rotating-shift workers are known to be a high-risk population for sleep disturbances; hypertension; gastrointestinal disturbances; obesity; and some cancers, including breast, colorectal, and prostate 3, 4, 5.

Circadian rhythms regulate hundreds of functions in the human body, including sleep and wake fullness, body temperature, blood pressure, digestive secretion, immune activity, and hormone production. Changes in circadian rhythms were proposed as a factor contributing to the observed increased in risk (3).

A previous study has showed an accelerated bone resorption in female rotating-shift workers because of perturbations of the diurnal rhythms of reproductive hormones (6). The present study was conducted to test the hypothesis that the chronic disruption in circadian rhythms observed in rotating-shift workers can lead to developed precocious osteoporosis.

Section snippets

Subjects

The study considered a total of 70 subjects: 39 were nurses who had worked a rotating shift, alternating night and day work during the last 10 yr (for each set of 3 day shifts and 1 night shift), and 31 were nurses who had worked only in the daytime in the last 10 yr. Eligible nurses were ambulatory postmenopausal older than 50 yr. All the activities performed in this study were conducted in accordance with the guidelines of The Declaration of Helsinki. All the participating individuals

Results

Clinical features, anthropometric variables, and laboratory findings of the participants according to the work schedule are shown in the Table 1. When comparing the 2 groups, women who worked in rotating shifts reported a higher prevalence of current smoking (48.7% vs 32.2%), coffee drinking (66.6% vs 16.1%), and a smaller number of children. The prevalence of family history of osteoporosis fracture and current alcohol drinking revealed no differences in magnitude.

The anthropometric and

Discussion

This study demonstrates that BMD is lower in the rotating-shift workers in comparison with daytime workers. A significant evidence was that rotating-shift work had an adverse effect on trabecular and cortical bone health. A previous study showed a great bone resorption (measured by urinary deoxypyridoline) in female rotating-shift workers; however, the BMD was not evaluated in this study (6). Several possible mechanisms could explain our results. Decreased exposure to daylight is known to

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: Dr. Ivan Quevedo received a grant DIUC #205.085.030.1-0 from University of Concepcion and one from Proyecto SAVAL for Clinic Research.

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Original ArticleLow Bone Mineral Density in Rotating-Shift Workers

Abstract

Introduction

Section snippets

Subjects

Results

Discussion

Nutrition

Shift-work sleep disorder—the glass more than half empty

N Engl J Med

Industrial shift systems

Appl Ergon

The circadian clock: pacemaker and tumor suppressor

Nat Rev Cancer

Night work and risk of breast cancer

Epidemiology

Original Article
Low Bone Mineral Density in Rotating-Shift Workers