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Shift work linked to higher coronary risk

People who work night shifts are 41% more likely to have a coronary event

Louise Prime

Friday, 27 July 2012

Working shifts is associated with an increased risk of suffering a major vascular event, an analysis involving more than two million people has shown. The steepest rise in risk of coronary events was linked with working night shifts, say the authors on bmj.com.

Shift work is acknowledged to disrupt the circadian rhythm and to be associated with an increased risk of hypertension, high cholesterol and diabetes, but debate has continued over its impact on risk of vascular disease. A team of researchers has now conducted the largest ever analysis of the subject.

Their systematic review and meta-analysis included 34 studies into the association between shift work and risk of myocardial infarction, ischaemic stroke and any coronary event, that included a total of 2,011,935 people. Between them, participants suffered 17,359 coronary events of some sort; 6598 had myocardial infarctions and 1854 had ischaemic strokes.

The researchers compared the rates of vascular events in non-shift (day) workers with the rates in people who worked evening shifts, irregular or unspecified shifts, mixed schedules, night shifts and rotating shifts.

They found that shift work was associated with a 23% increase in risk of heart attack, 24% increased risk of coronary events and 5% increased risk of stroke. The increased relative risks remained significant after adjusting for study quality, socioeconomic status and shift workers’ unhealthy behaviours. People who worked night shifts were 41% more likely than controls to suffer a coronary event.

Shift work was not associated with an increase in risk of either vascular or all-cause mortality.

The authors write: “Shift work is associated with myocardial infarction, coronary events, and ischaemic stroke; the relative risks are modest, but population attributable risks are high.”

They conclude: “Our findings have several implications. The increased risk of vascular disease apparent in shift workers, regardless of its explanation, suggests that people who do shift work should be vigilant about risk factor modification.

“Screening programmes for modifiable risk factors in shift workers have yielded substantial burdens of treatable risk factors, including dyslipidaemia, smoking, glucose intolerance, and hypertension. Shift workers should be educated about cardiovascular symptoms in an effort to forestall or avert the earliest clinical manifestations of disease.”

They suggest that modification and rationalisation of shift schedules might lead to healthier, more productive workers, although any potential long-term impact on vascular risks is unknown.

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