Working rotating shifts increases the risk of type 2 diabetes in women, according to two prospective cohort studies published in December 2011 by Harvard School of Public Health scientists.
Previous studies have found that working rotating shifts is associated with various health concerns, such as weight gain and metabolic syndrome. So it makes sense that this new study found equally harmful effects.
Researchers evaluated 69,269 women aged 42 to 67 years old who were participating in the Nurses’ Health Study I, and 107,915 women aged 25 to 42 years in the in Nurses’ Health Study II. The researchers determined at the beginning of the study how long the subjects had worked rotating shifts, defined as at least three nights per month in addition to days and evenings in that month. This was updated every two to four years in the Nurses’ Health Study II group. The study authors also administered a validated questionnaire to the subjects that confirmed self-reported type 2 diabetes.
According to the study, shift work was associated with an increase in the likelihood of type 2 diabetes. The subjects who reported working rotating shifts for one to two years had an increase in the likelihood of type 2 diabetes by five percent. Subjects who worked rotating shifts for three to nine years had their risk of type 2 diabetes increase by 20 percent, while 10 to 19 years of rotating shifts was associated with a 40 percent increased risk and 20 or more years with a 58 percent risk.
The researchers concluded that an extended period of rotating night shift work is associated with a modestly increased risk of type 2 diabetes in women, which appears to be partly mediated through body weight.
Previous research also indicated that low levels of melatonin, the key hormone that regulates circadian rhythms, are associated with suboptimal blood sugar metabolism. Furthermore, melatonin is a potent antioxidant and protects the pancreatic beta-cells that secrete insulin from oxidative damage.