Abstract
BACKGROUND:
We investigated how night shift duration and sleep problems were jointly associated with disabling low back pain (LBP) among workers in different occupations.
METHODS:
An online-survey was conducted regarding work schedules, disabling LBP, sleep problems, and other relevant factors in 5,008 workers who were randomly selected from a market research panel. Multiple logistic regression analyses determined the joint associations of night shift duration (0 [permanent day shift], <8, 8-9.9, 10-15.9, ≥16 hr) and sleep problems (no, yes) with disabling LBP adjusted for potential confounders.
RESULTS:
A night shift ≥16 hr was associated with a significant increase in the likelihood of disabling LBP. The magnitude of this association was elevated when participants perceived sleep problems including both sleep duration and quality.
CONCLUSION:
Associations between extended night shifts and disabling LBP became stronger in the presence of short or poor quality sleep.
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From the full-text paper:
- “The present study indicated that an extended night shift, particularly beyond 16 hr, was associated with a significant increase in the likelihood of disabling LBP. The magnitude of this association increased when participants perceived sleep problems.” (pg. 6);
- Regarding sleep duration, “a significantly greater OR for disabling LBP was obtained with sleep of less than 6 hr.” (pg. 6);
- For sleep quality, “a significantly increased OR [odds ratio] was found for cases where insomnia symptoms were reported.” (pg. 6).
The authors suggest several pathways in which extended night shifts and reduced sleep may be associated with increased likelihood of disabling LBP. One is a reduced threshold to pain following sleep restriction.
Another is that sleep disturbance can affect the “autonomic, neuroendocrine, and neuroimmunologic systems to provoke inflammatory response, delayed recovery of tissue damage, and increased pain sensitivity” (pg. 8). Another factor may be the increased exposure to mechanical loading and mental workload during the prolonged shift; which may further impact on sleep and continue the cycle.
Finally, the authors noted several study limitations. The study was cross-sectional and could not examine the temporal nature of study variables. Sleep data was collected by subjective measures and not objectively. Another was the small sample size of shift workers, which may have been biased due to the nature of survey (e.g. people with severe LBP or long/demanding schedules may have been less likely to take part); wide confidence intervals were also reported. Thus the authors suggest that these findings be viewed as preliminary.
Authors: Takahashi, M., Matsudaira, K., & Shimazu, A. (2015). Am J Ind Med.
Study link: https://doi.org/10.1002/ajim.22493
Link to the LinkedIn article: https://www.linkedin.com/pulse/disabling-low-back-pain-associated-night-shift-sleep-ben-hutchinson
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