If you are not naturally a night owl, you might want to rethink taking that night shift or other jobs with schedules outside of the norm. They could be hazardous to your health. However, dragging yourself out of bed at the crack of dawn can be equally risky for some.

New research has found that spending periods of time working during hours that are not in line with your natural body clock can put your cardiovascular system in jeopardy.

“Our study found that for each hour the work schedule was out of sync with an employee’s body clock, the risk of heart disease got worse,” said Dr. Sara Gamboa Madeira, the study’s author.

This discrepancy with the body’s clock happens when there is a mismatch between a worker’s biological rhythm, their natural sleep and waking habits, and their daily (or nightly) work schedule. Circadian rhythms vary from person to person.

Dr. Gambao Madeira explains, “We all have an internal biological clock which ranges from morning types (larks), who feel alert and productive in the early morning and sleepy in the evening, to late types (owls), for whom the opposite is true – with most of the population falling in between. Circadian misalignment occurs when there is a mismatch between what your body wants (e.g. to fall asleep at 10 pm) and what your social obligations imposed on you (e.g. work until midnight).”

For this study, researchers examined over 300 warehouse workers who filled out a variety of shifts at the same workplace, from six a.m. to three pm, three pm to midnight, or nine pm to six am.

Participants filled out surveys about their education, sex and age as well as work schedule and lifestyle factors. They also had their blood pressure and cholesterol measured.

Researchers then evaluated how long the participants slept and their individual internal biological clocks. This was used to calculate social jet lag – the number of hours of sleep sacrificed in order to participate in activities out of synch with one’s work schedule. Researchers separated the study participants into three groups according to their hours of social jetlag: 2 hours or under, 2–4 hours and 4 or more hours.

The greater social jetlag workers experienced, the higher their chances of being in danger of heart troubles. For every added hour of social jetlag, researchers found a 31 percent increase in risk of being classified as high cardiovascular risk.

“These results add to the growing evidence that circadian misalignment may explain, at least in part, the association found between shift work and detrimental health outcomes,” Dr. Gamboa Madeira said. “The findings suggest that staff with atypical work schedules may need closer monitoring for heart health.”

She went on to suggest that perhaps we align working shifts with the natural sleeping patterns of the employees. Night owls would be psychologically and physiologically healthier having night shifts and morning people should try to remain with the traditional nine-to-five.

One of the benefits of the current trend toward working remotely is that employees have a much greater amount of flexibility as to when they do the bulk of their work, so long as the work gets done. This makes regulating your sleeping and working times to your natural rhythms much easier.

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