Why a four-day work week might not be good for your health

The math is simple: working five eight-hour shifts is equivalent to working four 10-hour shifts. That’s true. But the implications of these schedules are different. The danger is in disregarding the health effects that can occur as a result of fatigue and stress that accumulate over a longer-than-normal working day.

I performed a study showing that the risk of suffering an industrial accident is raised by 37 percent for employees working more than 12 hours in a day. The risk is 61 percent higher for people in “overtime” shifts. Working more than 60 hours in a week is related to an additional injury risk of 23 percent. As the hours worked in those schedules increase, the risks grow accordingly.

More recently, Dr. Xiaoxi Yao, a colleague of mine who is now at the Mayo Clinic, and I recently performed another study using 32 years of work-hour information to analyze the relationship between long working hours over many years and the risk of being diagnosed with a chronic disease later in life. We found that the dangers were quite substantial, especially for women.

Women working more than 60 hours per week, equivalent to 12 hours per day, were more than three times as likely to eventually suffer heart disease, cancer, arthritis or diabetes, and more than twice as likely to have chronic lung disease or asthma, as women working a conventional 40-hour workweek. Working just a bit more, an average of 41 to 50 hours per week, over many years appeared to substantially increase the long-term risk of disease.