Rotating shift work, or working hours that change according to a set schedule, has been found to have a variety of impacts on health, from insomnia, to gastrointestinal disturbances, to worsening of conditions such as diabetes and epilepsy. Some studies have also linked rotating shifts to cardiovascular disease, and some evidence links this type of work with certain kinds of cancer (although this evidence is inconclusive).
Now, researchers at Harvard Medical School have found that rotating night shift work can increase women’s risk of developing Type 2 diabetes by almost 60%. According to the US Centers for Disease Control and Prevention, approximately 15 million Americans work permanent or rotating night shifts.
The researchers looked at data from roughly 70,000 women ages 42 to 67 from the Nurses Healthy Study I, tracked from 1988 to 2008, and approximately 108,000 women ages 25 to 42 from the Nurses Health Study II, tracked from 1989 to 2007. Roughly 60% of the women involved had worked more than a year of rotating night shift work at the start of the study; about 11% of the women in the Nurses Health Study I and 4% of the women in the Nurses Health Study II had worked rotating night shifts for more than 10 years at the study’s start, with the percentages increasing over time.
The researchers discovered that the longer women worked rotating night shifts, the greater their risk of developing Type 2 diabetes. Women who had worked these shifts for 3 to 9 years had a 20% increased risk; those who’d worked rotating night shifts for 10 to 19 years had a 40% increased risk; and those who’d worked these shifts for over 20 years had a 58% increased risk. Taking body weight into account, those who’d worked rotating night shifts for over 20 years still had a 24% increase in risk. (In a secondary analysis of the participants, night shift work was also associated with weight gain.)
According to lead study author An Pan, PhD, “Long-term rotating night shift work is an important risk factor for the development of Type 2 diabetes and this risk increases with the numbers of years working rotating shifts.” Senior author Frank B. Hu, MPH, MD, PhD, adds, “This study raises the awareness of increased obesity and diabetes risk among night shift workers and underscores the importance of improving diet and lifestyle for primary prevention of Type 2 diabetes in this high risk group.”
The study authors note that further research is needed to evaluate the effect of other shift work schedules, such as permanent evening or night shifts, on Type 2 diabetes risk, as well as to determine whether such an association between night shift work and Type 2 exists in men and in nonwhites (roughly 96% of the women in the study were Caucasian).
To learn more about the research, read the article “Rotating Night Shift Work Linked to Increased Risk of Type 2 Diabetes in Women, Study Finds” or see the study in the journal PLoS Medicine. And for more information about adjusting to shift work, see this piece from the Mayo Clinic.