Night-Shift Workers Have High Risk Of Diabetes Even after Retirement

People who regularly work night shifts in their lifetimes are twice as likely to have diabetes, even if they have retired and returned to a normal, daytime schedule, according to a study led by Timothy H. Monk, a professor of psychiatry at the University of Pittsburgh School of Medicine. The study’s results were published in the October 2013 Journal of Biological Rhythms. 

“The results are worrisome, given the current epidemic of diabetes and obesity in the U.S.,” said Monk. “Increasingly, scientific study has confirmed the importance of regular sleep patterns and sufficient sleep in maintaining good health.”

The research complements previous international studies that found night-shift work is associated with a decrease in metabolic health, impaired glucose metabolism, increased body mass index (BMI), and impaired insulin resistance. In the United States, a recent Nurses’ Health Study—a large National Institutes of Health-funded study begun in 1975 that tracks the health of registered nurses— showed a night-shift work-related increase in BMI and diabetes risk in working female nurses. Monk’s study is the first to examine the increased risk of diabetes in a large, U.S. sample of retired men and women with varying preretirement occupations who are no longer subject to the stresses of night-shift work.

Researchers interviewed more than 1,000 retired night-shift workers over 65-years-old living in western Pennsylvania. The respondents were divided into five groups: those who worked night shifts for 0 years, 1 to 7 years, 8 to 14 years, 15 to 20 years, and more than 20 years. The results follow.

• Both BMI and diabetes rates were higher in retired former night- shift workers than in retired former day workers.
• Night-shift retirees with higher BMIs were about twice as likely as retired former day workers to be diabetic.
• Even when BMI was excluded as a factor, diabetes risk was still higher in retired night-shift workers (1.4 times greater risk as opposed to 2 times greater risk).
• Diabetes risk within the five shift-work-exposed groups did not differ, suggesting that any exposure to night-shift work can be associated with increased risk. 

“We ought to recognize that there is a health cost to society of exposing large numbers of people to night-shift work,” added Monk. “Steps should be taken both to encourage day work as an alternative wherever possible and also to provide education and support for employees who are in occupations that, by their very nature, require work at night.”

The authors also recommended that intensive educational campaigns be launched to encourage night-shift workers to adopt behavioral strategies regarding diet, exercise, and circadian adjustment because of their increased vulnerability to metabolic health problems.