Study Links Shift Work to Risk for Type 2 Diabetes
Researchers cite many possible reasons for the effect, including hormonal changes
By Mary Elizabeth Dallas
THURSDAY, July 24, 2014 (HealthDay News) -- Shift workers, especially men, may be at higher risk for type 2 diabetes compared to people not on such schedules, a new study suggests.
Also at special risk are shift workers who don't work on a set schedule, with shifts moving around at various times of the day.
The findings are "not at all surprising," said one expert, Dr. Alan Manevitz, a clinical psychiatrist at Lenox Hill Hospital in New York City.
"Physicians have long known that working shifts disrupts many key body chemicals, creating a ripple effect that can lead to ailments such as gastrointestinal disorders, cardiovascular disease and even cancer," he said. "Now type 2 diabetes can be added to this considerable list."
In the new review, researchers analyzed data from 12 international studies involving more than 226,500 people.
The study, led by Zuxun Lu of Huazhong University of Science and Technology in Wuhan, China, took several factors into account, such as workers' shift schedules, their body mass index (BMI, a calculation of height and weight), family history of diabetes and their level of physical activity.
Although the findings weren't able to show a direct cause-and-effect relationship, the researchers found that any amount of shift work was linked to a 9 percent greater risk for developing diabetes. Gender also played a role -- for men engaged in shift work, the risk jumped to 37 percent.
Although the reason why men are at greater risk than women isn't clear, the researchers believe that testosterone levels may play a role. Prior studies have pointed to an association between low testosterone levels and insulin resistance and diabetes, the researchers noted.
Daytime levels of this male hormone are regulated by the internal body clock, Lu's team explained.
Those whose shifts moved around through different periods of the day were especially likely to develop type 2 diabetes than those who worked normal "office hours." The study found rotating shift work to be linked to a 42 percent greater risk for diabetes.
According to Lu's team, erratic working schedules make it more difficult for the body to establish a sleep-wake cycle, and poor sleep may worsen insulin resistance, a precursor to diabetes.