Night Shift Workers At Increased Risk Of Heart Attack, Stroke
July 27, 2012

Night Shift Workers At Increased Risk Of Heart Attack, Stroke

Lawrence LeBlond for - Your Universe Online

People who regularly do shift work are slightly more at risk of having a heart attack or stroke than their day-only working counterparts, according to research published in the British Medical Journal.

According to researchers from Norway and Canada, heart attack and stroke can be added to the list of previously known risks of shift work, risks that include high blood pressure, diabetes and obesity. The researchers defined shift work as evening shifts, irregular shifts, mixed schedules, overnight shifts, and rotating shifts.

The study involved the analysis of more than 2 million workers from 34 studies, is the largest analysis of shift work and vascular risk to date, and has implications for public policy and occupational medicine.

The vascular link to shift work has been controversial, so researchers decided to take on the project to either confirm or deny an association.

Among the 2,011,935 people across the studies, 17,359 had some type of coronary event, 6,598 had heart attacks, and 1,854 had ischemic strokes caused by lack of blood to the brain. They found that these events were more common among shift workers than day (non-shift) workers. Shift workers experienced a 23 percent increased risk of heart attack, a 24 percent increased risk of some coronary event, and a 5 percent increased risk of stroke.

The risks remained consistent even after taking into consideration a number of factors, including study quality, socioeconomic status and unhealthy behaviors in shift workers.

The study authors said shift workers should know the risks that come with the schedule they keep. “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,” the authors wrote in the report.

They note, however, that a variety of factors -- not just the shift work itself -- could be playing into the increased risk of vascular events. A lack of sleep, poor eating habits and decreased physical activity could also be key to driving up the risks of heart attack and stroke.

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.

Of all the different shift work types, night shifts were associated with the highest increased risk for coronary events (41 percent). However, despite the increased risks associated with shift work, the study authors found no increased mortality rates in these groups.

Dr. Carl Lavie, a cardiologist at Ochsner Medical Center in New Orleans, explained that disruption in circadian rhythm, a common feature inherent in shift work, can be one factor in unfavorable health risks. These disruptions can certainly have an effect on heart rate and blood pressure -- two measures intimately tied to vascular health.

Since shift work is necessary for more than a third of the working population, it is unreasonable to think that everyone can simply change their schedules, he noted.

“My advice would be to exercise and make sure their fitness is at a high level, and then I'd treat their risk factors vigorously," Lavie told ABC News℠ Stacey Schott.

Dr. Robert Bonow, professor of medicine at Northwestern University Feinberg School of Medicine, agreed. “There's somewhat of a signal here, and people who do shift work should be aware that their risk factors should be identified and managed.”

The study authors say that screening programs could help identify and treat risk factors for shift workers. They could also be educated about what symptoms to look out for, which may indicate early heart problems.

Jane White, research and information services manager at the Institution of Occupational Safety and Health, said issues associated with shift work, such as “disturbed appetite and digestion, reliance on sedatives and, or stimulants, as well as social and domestic problems” all have a negative impact on work. “These can affect performance, increase the likelihood of errors and accidents at work, and even have a negative effect on health.”

White told BBC News the effects of shift work need 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.”

The increased risks involved with shift work are “relatively small,” according to Ellen Mason, senior cardiac nurse at the British Heart Foundation. But workers can make positive changes in their health no matter what shifts they work. “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.”