Shift work is associated with an increased risk of major vascular problems, such as heart attacks and strokes, according to a new Canadian-led study.
Shift work is linked to a 23 per cent increased risk of heart attack, 24 per cent increased risk of coronary event and five per cent increased risk of stroke, found the study, led by Daniel Hackam, a clinical pharmacologist at the Stroke Prevention & Atherosclerosis Research Centre in London, Ont.
Night shifts are associated with the steepest increase in risk for coronary events (41 per cent).
A team of international researchers analyzed the results of 34 studies involving over two million individuals to investigate the association between shift work and major vascular events. Shift work was defined as evening shifts, irregular or unspecified shifts, mixed schedules, night shifts and rotating shifts.
The study, published in the British Medical Journal, is the largest analysis of shift work and vascular risk to date.
Shift work has long been known to disrupt the body clock (circadian rhythm) and is associated with an increased risk of high blood pressure, high cholesterol and diabetes, but its association with vascular disease is controversial, say the authors.
The frequency of shift work in the general population means that the overall risks are high. In Canada — where 32.8 per cent of workers were on shifts during 2008-09 — seven per cent of heart attacks, 7.3 per cent of all coronary events and 1.6 per cent of ischaemic strokes could be attributed to shift work, found the study.
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