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Most of us sympathise with shift workers because of the inconvenience of dinner at 2 a.m. or the angst of passing your spouse in the hallway every morning. But evidence is mounting that there are very real health consequences, too.

New Canadian research suggests that women who work night shifts may face an increased risk of heart disease, according to a piece from the CBC. (Previous research has also linked shift work with breast cancer.)

Researcher Joan Tranmer — who spent 30 years as a nurse — and a team of researchers from Queen's University in Kingston, found that about one in five middle-aged women who do shift work has at least three of the risk indicators for heart disease. These include abdominal obesity, high blood pressure and low levels of HDL or "good" cholesterol, according to the CBC.

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"Just how shift work contributes to the development of such risk factors isn't clear," Ms. Tranmer told the CBC. "It is possible that the disruption of biological rhythms, sleeping, eating, and exercise patterns may be factors."

The researchers looked at a group of 227 women between the ages of 22 and 66 who worked at two Ontario hospitals as nurses, administrative employees and lab and equipment technicians in a range of shift rotations, the CBC reported.

Within the group, 17 per cent had three identified risk factors, said the report. Almost 40 per cent had high blood pressure and 60 per cent had a high waist circumference, indicating abdominal obesity, the most worrisome kind of obesity according to experts.

Another recent Canadian study, again from Queen's, found that as bad as they may be, irregular shifts may also be a step up from constantly doing the graveyard shift.

This study measured worker's levels of melatonin, "a hormone that has been shown to prevent cancer development," reported the Vancouver Sun.

Melatonin is predominantly produced by the body at night, peaking between midnight and 4 a.m., according to the Sun report.

"Nurses who worked two 12-hour day shifts, then two 12-hour night shifts in dimly lit hospital wards before taking a five-day break had similar melatonin levels regardless of when they worked," the authors of the paper wrote.

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It appears that having some day shifts may mitigate the harm of night shifts.

"If melatonin is one of the factors causing an increase in cancer risk for people who do shift work — and that's still an open question — then it's possible that this shift pattern might be better for health," one of the researchers told the Sun.

While researchers work out the details, should workplaces take the health risks of shift work — especially the night shift — more seriously?

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