2012-07-27 03:55:14
27 July 2012 Last updated at 00:14 GMT
Shift workers are slightly more at risk of having a heart attack or stroke than day workers, research suggests.
An analysis of studies involving more than 2m workers in the British Medical Journal said shift work can disrupt the body clock and have an adverse effect on lifestyle.
It has previously been linked to an increased risk of high blood pressure and diabetes.
Limiting night shifts would help workers cope, experts said.
The team of researchers from Canada and Norway analysed 34 studies.
In total, there were 17,359 coronary events of some kind, including cardiac arrests, 6,598 heart attacks and 1,854 strokes caused by lack of blood to the brain.
These events were more common in shift workers than in other people.
The BMJ study calculated that shift work was linked to a 23% increased risk of heart attack, 24% increased risk of coronary event and 5% increased risk of stroke.
But they also said shift work was not linked to increased mortality rates from heart problems and that the relative risks associated with heart problems were "modest".
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Ensuring workers have a minimum of two full nights sleep between day and night shifts can help people to cope with shift work.
Jane White Institution of Occupational Safety and Health
The researchers took the socioeconomics status of the workers, their diet and general health into account in their findings.
No rest
Dan Hackam, associate professor at Western University, London Ontario in Canada, said shift workers were more prone to sleeping and eating badly.
"Night shift workers are up all the time and they don't have a defined rest period. They are in a state of perpetual nervous system activation which is bad for things like obesity and cholesterol," he said.
The authors say that screening programmes could help identify and treat risk factors for shift workers, such as high blood pressure and cholesterol levels.
They add that shift workers could also be educated about what symptoms to look our for, which might indicate early heart problems.
Jane White, research and information services manager at the Institution of Occupational Safety and Health, said there are complex issues surrounding shift work.
"It can result in disturbed appetite and digestion, reliance on sedatives and, or stimulants, as well as social and domestic problems.
"These can affect performance, increase the likelihood of errors and accidents at work, and even have a negative effect on health.
She said the effects of shift work needed to be well-managed.
"Avoiding permanent night shifts, limiting shifts to a maximum of 12 hours and ensuring workers have a minimum of two full nights sleep between day and night shifts are simple, practical solutions that can help people to cope with shift work."
Ellen Mason, senior cardiac nurse at the British Heart Foundation, said the increased risk to an individual shift worker "was relatively small".
"But many Brits don't work nine to five and so these findings becomes much more significant.
"Whether you work nights, evenings or regular office hours, eating healthily, getting active and quitting smoking can make a big difference to your heart health."