Increased type 2 diabetes risk for black women working night shifts

Tue, 13 Jan 2015
Black women working night shifts are at an increased risk of developing type 2 diabetes compared to women not working at nights, a study suggests.

Researchers from the Slone Epidemiology Centre in Boston University analysed data from the Black Women's Health Study (BWHS) to assess why diabetes is twice is prevalent in black women (12.2 per cent) than white women (4.5 per cent) in the United States.

They compared over 28,000 black women aged between 21 and 69 from 2005. All women were free of diabetes and were followed for eight years.

During the follow-up period, roughly 1,800 cases of diabetes were diagnosed. 37 per cent of the group reported to have undertaken some night shift work. Shift work was either in the form of a regular work pattern at an unusual time of the day, or scattered working hours.

The amount of years spent working night shifts played a role in the increased risk of developing diabetes. The following risk percentages were identified by the researchers:
  • 1-2 years of night shifts - 17% risk of diabetes
  • 3-9 years of night shifts - 23% risk of diabetes
  • 10+ years of night shifts - 42% risk of diabetes

Circadian system disruption

The findings were adjusted to account for variables such as BMI, smoking status and diet, with the associated risk of diabetes still significant.

"These atypical work patterns may perturb the circadian system, which is entrained most powerfully by the solar light-dark cycle and modulates daily rhythms in alertness, core body temperature, heart rate, blood pressure and neurotransmitter and hormone secretion," the authors wrote.

The researchers believe this discovery is significant in illustrating how the disruption of circadian rhythm and sleep deprivation can increase the risk of diabetes.

"Our findings from the Black Women's Health Study contribute to the observational literature that consistently demonstrates a relationship between disruption of circadian rhythms and long-lasting adverse effects on metabolism, such as obesity and type 2 diabetes mellitus," said study lead author Dr. Varsha G. Vimalananda.
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