Impact of a Longer Work Week on Diabetes Incidence

A team of Canadian researchers sought to determine if working at least 45 hours per week had an effect on the incidence of diabetes.

A longer workweek has not been associated with an increased risk of diabetes among men, but women working ≥45 hours per week are significantly more at risk, according to a recent study published in BMJ Open Diabetes Research & Care.

Long work hours have lately been considered a risk factor for the development of diabetes, but extensive evidence has yet to confirm this theory. Thus, researchers used a nationwide database to evaluate workers aged 35 to 74 years (N=7065 [women=3502; men=3564]) in Ontario, Canada, over a 12-year period.

The study’s primary outcome was incident diabetes, defined as one hospital admission with a diabetes diagnosis or 2 physician service claims with a diagnosis of diabetes in a 2-year period. The researchers grouped work hours (paid and unpaid) into 4 categories:  13 to 34 hours, 35 to 40 hours, 41 to 44 hours, and ≥45 hours per week.

In addition to workload, the researchers assessed participants for several other variables such as living location, self-reported chronic medical conditions, work shift schedule, and body posture/movement.

Over the study period, 10% of the total population developed diabetes (12.2% of men and 7.5% of women). Older, obese participants had the highest incidence rate. Compared with women who worked 41 to 44 hours per week, those who worked ≥45 hours weekly were at significantly greater risk of developing diabetes (7.2% vs 8.5%).

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The opposite was true for men: diabetes incidence decreased as the number of work hours increased (17.6% for those who worked 15 to 34 hours per week vs 9.5% for those who worked ≥45 hours).

The researchers cited limitations to their study, including potential misclassification bias due to measuring work hours at only a single time point, as well as inability to distinguish between type 1 and type 2 diabetes.

Despite these and other limitations, the researchers said of their results, “Considering the rapid and substantial increase of diabetes prevalence in Canada and worldwide, identifying modifiable risk factors such as long work hours is of major importance to improve prevention and orient policy making, as it could prevent numerous cases of diabetes and diabetes-related chronic diseases.”


Gilbert-Ouimet M, Ma H, Glazier R, Brisson C, Mustard C, Smith P. Adverse effect of long work hours on incident diabetes in 7065 Ontario workers followed for 12 years [published online May 30, 2018] BMJ Open Diabetes Res Care. doi: 10.1136/ bmjdrc-2017-000496