Shift work and vascular events: systematic review and meta-analysis

 Did your doctor inform you that shift work needs to stop?

Shift work and vascular events: systematic review and meta-analysis

BMJ 2012; 345 doi: https://doi.org/10.1136/bmj.e4800 (Published 26 July 2012) Cite this as: BMJ 2012;345:e4800

• Article
• Related content
• Metrics
• Responses
• Peer review

1. Manav V Vyas, graduate student1,  
2. Amit X Garg, professor123,  
3. Arthur V Iansavichus, information specialist3,  
4. John Costella, research and instructional librarian4,  
5. Allan Donner, professor15,  
6. Lars E Laugsand, PhD candidate6,  
7. Imre Janszky, researcher67,  
8. Marko Mrkobrada, assistant professor25,  
9. Grace Parraga, associate professor8,  
10. Daniel G Hackam, associate professor125

Author affiliations

1. Correspondence to: D Hackam, Stroke Prevention and Atherosclerosis Research Centre (SPARC), Room 100K-2, Siebens Drake Research Building, 1400 Western Road, London, ON, Canada N6G 2V2 dhackam@uwo.ca

• Accepted 21 June 2012

Abstract

Objective To synthesise the association of shift work with major vascular events as reported in the literature.

Data sources Systematic searches of major bibliographic databases, contact with experts in the field, and review of reference lists of primary articles, review papers, and guidelines.

Study selection Observational studies that reported risk ratios for vascular morbidity, vascular mortality, or all cause mortality in relation to shift work were included; control groups could be non-shift (“day”) workers or the general population.

Data extraction Study quality was assessed with the Downs and Black scale for observational studies. The three primary outcomes were myocardial infarction, ischaemic stroke, and any coronary event. Heterogeneity was measured with the I² statistic and computed random effects models.

Results 34 studies in 2 011 935 people were identified. Shift work was associated with myocardial infarction (risk ratio 1.23, 95% confidence interval 1.15 to 1.31; I²=0) and ischaemic stroke (1.05, 1.01 to 1.09; I²=0). Coronary events were also increased (risk ratio 1.24, 1.10 to 1.39), albeit with significant heterogeneity across studies (I²=85%). Pooled risk ratios were significant for both unadjusted analyses and analyses adjusted for risk factors. All shift work schedules with the exception of evening shifts were associated with a statistically higher risk of coronary events. Shift work was not associated with increased rates of mortality (whether vascular cause specific or overall). Presence or absence of adjustment for smoking and socioeconomic status was not a source of heterogeneity in the primary studies. 6598 myocardial infarctions, 17 359 coronary events, and 1854 ischaemic strokes occurred. On the basis of the Canadian prevalence of shift work of 32.8%, the population attributable risks related to shift work were 7.0% for myocardial infarction, 7.3% for all coronary events, and 1.6% for ischaemic stroke.

Conclusions Shift work is associated with vascular events, which may have implications for public policy and occupational medicine.