Shift work associated with vascular events

People who work any schedule other than a standard day or evening shift have an increased risk of major vascular events, according to a meta-analysis.

Canadian researchers assessed 34 observational studies with more than 2 million participants. The included studies used prospective cohorts, retrospective cohorts or case controls to compare shift workers (those who worked all evenings or nights, or irregular, mixed or rotating shifts) to either daytime workers or the general population. Results were published by BMJ on July 26.

All of the shift work schedules except evening shifts were associated with a higher risk of coronary events. Shift workers had a 23% higher risk of myocardial infarction (risk ratio [RR], 1.23; 95% CI, 1.15 to 1.31) and a 5% higher risk of stroke (RR, 1.05; 95% CI, 1.01 to 1.09). The risk of any coronary event was also increased (RR, 1.24; 95% CI, 1.10 to 1.39), but no association with mortality risk was found in the studies that assessed all-cause or cardiovascular mortality.

With its basis on observational data, the analysis cannot prove causality, the study authors noted. Shift workers have previously been found to have lower socioeconomic status and engage more in unhealthy behaviors, such as smoking, than daytime workers. However, the studies within this analysis that adjusted for socioeconomic status had similar findings to the overall results, the authors said, and other research has found that adjustment for unhealthy behavior does not eliminate the apparent risk of shift work.

Given these findings, and regardless of causality, shift workers and their physicians should be vigilant about modifying cardiovascular risk factors, the authors concluded. Screening and education programs can identify risk factors and possibly forestall or prevent disease. Modification of schedules may also improve the health of these workers, the authors said, although more research is needed to assess long-term effects of such strategies and to identify the workers at highest risk.