Findings were consistent with earlier studies that link long work hours and diabetes as well as long periods of sitting with diabetes and obesity.
Working 45 hours a week or more increases the risk of diabetes among women but not among men, according to a 12-year study of Canadians.
The study, appearing in BMJ Open Diabetes Research and Care, confirms earlier findings that linked long work hours with the disease, but many earlier studies looked at women or men only. This new study also examines the effect of working just a few hours longer than a 40-hour week, compared with working 45 hours or more.
More than 30 million Americans have diabetes, and the cost of the disease now exceeds $327 billion, a jump from $245 billion in 2012, according to the American Diabetes Association. The United States is not alone in confronting the rising costs of the disease, and the Canadian researchers expressed alarm at rising incidence in their country.
For this study, researchers led by Mahee Gilbert-Ouimet, PhD, examined identified 7065 Ontario residents who took part in 2003 Canadian Community Health Survey and linked their data with health records covering a 12-year period. The respondents were 35 to 74 years old.
Working beyond 40 hours a week did not increase the risk of diabetes among men. But women who worked 45 hours or more per week had a significantly higher risk (63%) of developing diabetes. The effect of long work hours was only slightly mitigated when researchers adjusted for whether workers smoked, drank too much alcohol, reported getting exercise, or had high a body mass index.
Women who worked 35 to 40 hours per week did not have an elevated risk for diabetes, and those working 41 to 44 hours per week had slight increased risk (13%), but less than those working longer.
Researchers discussed possible reasons for the difference between men and women. They noted that more than one-third of the men in the study (36%) said they had jobs that required combinations of sitting, standing, and walking, which have been showed to reduce the risk of heart disease.
Working long hours is thought to bring about a chronic stress response, which speeds up hypothalamic-pituitary activity, boosting glucocorticoids, and cortisol levels. This in turn contributes to insulin resistance and glucose intolerance, as well as obesity. Multiple studies link long periods of sitting with elevated risk of diabetes and obesity.
The authors wrote the recent evidence suggests that the combination of work stress and family responsibilities at home “may intensify the tendency of adults working long hours to engage in unhealthy behaviors, experiencing difficulties with sleeping, and have poor mental health.”
They note this is an observational study, and it is not possible to establish a cause and effect from looking at the data. More work should be done in this area, they wrote.
Gilbert-Ouimet M, Ma H, Glazier R, et al. Adverse effect of long work hours on incident diabetes in 7065 Ontario workers followed for 12 years. BMJ Open Diab Res Care. 2018;6:e000496. doi:10.1136/bmjdrc-2017-000496.