Rotating Shift Work May Boost Women's Diabetes
TUESDAY, Dec. 6 (HealthDay News) -- Working rotating night
shifts may do more than leave you tired; it may also increase your
risk of developing type 2 diabetes, new research finds.
A study of two groups of women found that those who worked
rotating night shifts were more likely to develop type 2 diabetes
than women with regular hours, and the longer that they worked a
rotating shift schedule, the greater their risk.
"The association is quite strong and very consistent between the two cohorts," said the study's senior author, Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.
"For nurses who spent a couple of years working rotating night shifts, there was a minimal increase in risk. But, for those with a very long duration of rotating shifts, the risk was almost 60 percent higher. This provides pretty strong evidence that the longer the rotating night shift work, the greater the risk of diabetes," Hu said.
Results of the study are published in the December issue of
Rotating shift work is becoming more common, according to
background information in the study. Several studies have found a
link between these varying or unusual work schedules and obesity
and metabolic syndrome (a group of symptoms, such as high blood
pressure and insulin resistance, linked to a higher risk of heart
disease). Both factors are associated with an increased risk of
type 2 diabetes. Recently, a few studies on Japanese men found a
link between working the night shift and type 2 diabetes, according
to the study.
For the current study, rotating shift work was defined as
working three or more nights a month, plus days and evenings. Hu
and his team looked at data from two groups of women involved in
the U.S. Nurses' Health Studies I and II. There were more than
69,000 women between the ages of 42 and 67 in the first study, and
nearly 108,000 women between the ages of 25 and 42 in the second
When the women enrolled in the trials, none had diabetes,
cardiovascular disease or cancer.
During the 18- to 20-year study period, 6,165 women in the first
group and almost 4,000 women from the second group developed type 2
When compared to women who hadn't done rotating shift work,
women who did one to two years of shift work had a 5 percent
increase in type 2 diabetes. Women who worked shifts for three to
nine years had a 20 percent increased risk, while women who toiled
10 to 19 years on rotating shifts had a 40 percent greater risk of
type 2 diabetes compared to women who didn't do shift work.
Women with more than 20 years on a rotating work schedule had
the highest risk of all, with a 58 percent increase in the risk of
type 2 diabetes, the study found.
When the researchers adjusted the data to account for body mass,
the association between shift work and type 2 diabetes was reduced,
but still present, they said.
Although the study wasn't designed to figure out why rotating
shift work might increase the risk of type 2 diabetes, Hu said
there are likely both biological and behavioral reasons. Rotating
shift work disturbs the body's natural time clock (circadian
rhythm), which, in turn, disrupts the body's ability to balance its
need for energy. Hu said this can cause higher levels of glucose
and insulin resistance, which are hallmarks of type 2 diabetes.
Working on rotating shifts also affects eating and sleeping
behaviors, and women who worked rotating shifts also tended to
"Shift work is an important risk factor for obesity and type 2 diabetes," Hu said. "This study increases the awareness of diabetes risk among people who work on a rotating shift, and the importance of diabetes screening, detection and prevention in this high risk group."
More research is needed to confirm the findings, the authors
Worldwide, about 346 million people have diabetes. Most of them
suffer from type 2 diabetes, typically caused by excess body weight
and physical inactivity. Over time, the disease can damage vital
organs, including kidneys, nerves and heart.
Dr. Joel Zonszein, director of the clinical diabetes center at
Montefiore Medical Center in New York City, said other influences
besides work hours may have contributed to the development of
diabetes among the study participants.
"This study shows an association between working night shifts and obesity and diabetes. But, it's difficult to disassociate other risk factors," Zonszein said. "It may not just be that they work at night. They may work harder; they may be more stressed. There was more smoking. All of these things are related."
Learn more about preventing diabetes from the
American Diabetes Association.
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