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Shift work and ischaemic heart disease: meta-analysis and dose-response relationship.

BACKGROUND
Shift work is common in many industries. The potential association between shift work and ischaemic heart disease (IHD) remains controversial.


AIMS
To conduct a systematic review and meta-analysis of epidemiological evidence and summarize the potential relationship between shift work and IHD.


METHODS
We searched all relevant case-control and cohort studies that were published from January 1970 to October 2017 on PubMed, Web of Science and Embase. The random-effects model and the generalized least-squares trend model were, respectively, used to evaluate the pooled relative risk and dose-response relationship between shift work and IHD. Two different authors extracted data and assessed the quality of each study independently.


RESULTS
Twenty-one articles with 31 independent results of 19 782 IHD cases in 320 002 participants were included. The pooled relative risk for the association between shift work and risk of IHD was 1.13 (95% CI 1.08-1.20, I2 = 53%, P < 0.001). Further evaluation of dose-response relationship indicated that each 1-year increase in shift work was associated with 0.9% (RR = 1.009; 95% CI 1.006-1.012) increase of the risk of IHD.


CONCLUSIONS
This meta-analysis updated the evidence that shift work was associated with the risk of IHD and supported a positive dose-response relationship between the risk of IHD and increasing duration of shift work.