Clocking up 45 or more working hours in a week is linked to a heightened risk of diabetes in women, according to an observational study in Canada.
However, sticking to a working week of 30 to 40 hours may help to curb any increase in risk of developing the condition, suggest the researchers in the journal BMJ Diabetes Research and Care.
“A higher incidence of diabetes was observed among those working more than 40 hours per week”
They noted that previous research had indicated a link between long working hours and heightened diabetes risk, but most of these studies have focused exclusively on men.
To shed more light, the researchers tracked the health of 7,065 Canadian workers between the ages of 35 and 74 over a period of 12 years, using national health survey data and medical records.
Weekly paid and unpaid working hours were grouped into four time bands – 15-34 hours, 35-40 hours, 41-44 hours, and 45 or more hours.
A range of potentially influential factors were analysed, including age, sex, marital status, parenthood, ethnicity, birth place and of residence, long-term conditions, lifestyle and body mass index.
Workplace factors, such as shift work, the number of weeks worked in the preceding 12 months, and whether the job was primarily active or sedentary, were also included in the analysis.
During the monitoring period, one in 10 participants developed type 2 diabetes, with diagnoses more common among men, older age groups, and those who were obese.
The length of the working week was not found to be associated with a heightened risk of the disease among men.
If anything, the researchers said the incidence of diabetes tended to fall the longer a man’s working week was. However, this was not the case among women in the study.
Among those who worked 45 or more hours a week, the risk was significantly higher (63%) than it was among those who worked between 35 and 40 hours.
In addition, the effect was only slightly reduced when factors, such as smoking, physical activity levels, alcohol consumption and BMI, were taken into account.
“Identifying modifiable risk factors such as long work hours is of major importance to improve prevention and orient policy making”
The study authors said: Over the study period, 10% of the study population developed diabetes, with a higher incidence among men (12.2%) than women (7.5%), older groups, and obese individuals.
“Among women, a higher incidence of diabetes was observed among those working more than 40 hours per week compared with those working fewer hours,” they stated.
“Conversely, among men, the incidence of diabetes rather tended to decrease as the number of work hours increased,” they said.
The researchers suggested that long working hours might prompt a chronic stress response in the body, so increasing the risk of hormonal abnormalities and insulin resistance.
They said: “Considering the rapid and substantial increase of diabetes prevalence 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.”