Many jobs require staff to work at night, but new research says working at this time of the day might increase the risk of heart diseases among employees.

Nursing employees may be asked to work at night. These medical personnel start their work day just when everybody else is already dreaming in their sleep. Unfortunately, this continuous work routine might be risky for such individuals insofar as having coronary heart disease (CHD) is concerned.

In a study headed by Dr. Celine Vetter of Brigham and Women's Hospital, Boston, findings indicated that even at least three nights of working shifts every month could increase the possibility of acquiring coronary heart disease within a course of 24 years.

The researchers used data from 189,000 women. Among the subjects, 40 percent were participating in the Nurses' Health Study (NHS) which started in 1988, while the other subjects were part of NHS2 which started in 1989.

The subjects aged 25 to 55 joined the study with no history of coronary heart disease. Over the course of the study, the participants working at night in NHS2 were constantly monitored every two years while NHS participants were only asked once as regards their history of night shifts.

The NHS study reported 7,303 cases of illnesses connected to heart diseases, while NHS2 reported 3,519 cases. Illnesses reported included chest pain, heart attacks and bypass surgeries.

"Over the course of the study period a little more than 10,000 cases of newly developed coronary heart disease occurred," said Vetter.

The study revealed that nurses working at night for less than five years are 12 percent prone to CHD. Nurses who worked night shifts from five to nine years are at higher risk for CHD at 19 percent, while nurses working at night for 10 years have a 27 percent risk.

"Rotating night shift work is associated with modest risk of coronary heart disease even after taking into account known risk factors such as elevated BMI, smoking, poor diet quality, and low levels of physical activity," said Vetter.

The research still could not explain the link between working at night and CHD cases but Vetter explained that it could be associated with increased social disruption and inflammation in the body.

Vetter added that the risk of having CHD may be applied to people working too early because they are also forced to wake up at night.

The researchers still need to gather more data to be able to formulate a healthy work schedule.

"Hopefully we can design schedules that are healthier for the individual," said Vetter.

The study was published April 26, 2016 in The Journal of American Medical Association (JAMA).

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