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Working night shifts may increase diabetes risk for black women
– Reported January 15, 2015
The study authors report that 35% of non-Hispanic black Americans work shifts.
The study, published in Diabetologia, utilized data from the Black Women’s Health Study (BWHS) – a large ongoing prospective cohort study.
According to background research in the study, over 8 million American are employed in shift work, including 35% of non-Hispanic black people. Shift work is defined by the authors as work that occurs outside of typical daytime working hours.
Shift work can either take the form of a regular work pattern occurring at an unusual time of day or working hours that regularly change.
“These atypical work patterns may perturb the circadian system,” write the authors, “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.”
Previous research has examined the association between night shift work and diabetes. In many cases, the association was largely attributed to the body mass index (BMI) of study participants, though this did not explain all incidences of the metabolic disorder.
In the US, diabetes is more than twice as prevalent among black women (12.2%) than white women (4.5%). This prevalence prompted the research, conducted by Dr. Varsha Vimalananda and colleagues.
Risk increase remained significant after adjusting for BMI
For the study, the authors analyzed data about working night shifts from the BWHS provided by 28,041 participants in 2005. All participants were free of diabetes at the start of the study and were subsequently followed by the researchers for the next 8 years. Incidences of diabetes were recorded during this time.
A total of 37% of participants reporting working a night shift, with 5% reporting working a night shift for at least 10 years. The researchers observed 1,786 cases of diabetes developing during the follow-up period.
The risk of developing diabetes increased according to the amount of years that had been spent working night shifts. The following risk percentages were found:
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1-2 years of night shifts – 17% risk of diabetes
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3-9 years of night shifts – 23% risk of diabetes
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10+ years of night shifts – 42% risk of diabetes.
When the authors adjusted their findings to account for potential confounders such as BMI, diet and smoking status, the association between night shift work and an increased diabetes risk remained significant. Working night shifts for 10 years or more was still associated with a 23% increase in diabetes risk compared with black women who had never worked those hours.
“Even though lifestyle factors and BMI explained a major part of the association of shift work with incident diabetes, women with a long duration of shift work had an increased risk of diabetes after control for those factors, suggesting the presence of additional causal pathways,” write the authors.
Age was also a factor, with younger women having a higher risk of diabetes than older women. In terms of working night shifts for 10 or more years, women younger than 50 had a 39% higher risk of diabetes compared with those that had never worked night shifts, whereas women aged 50 and over faced a 17% higher risk.
Shift work metabolic effects ‘strengthened’ with continuous sleep disruption
“The metabolic effects of long-term shift work likely underlie a part of the association with diabetes that we and others describe and that strengthens with years of exposure to sleep disruption,” state the study authors.
The study was limited by the use of self-reported diabetes diagnoses, although the authors state that a previous study found 96% of self-reported diabetes cases could be confirmed in medical records.
Shift work status was only reported at one point in time, at the beginning of the study, and so the working schedules of the study participants may have changed during the follow-up period. Future research could be conducted to verify the findings.
“In summary we found that African-American women undergoing long-duration night-shift work had a higher risk of incident diabetes,” conclude the authors.
“There is a need for continued research into facilitating circadian adaptation to shift work and consideration of avoiding shift work in favor of other work arrangements when possible.”
Previously, Medical News Today reported on another study that found women who work rotating night shifts for 5 years or more may be at an increased risk of all-cause, cardiovascular and lung cancer mortality.
source: http://www.medicalnewstoday.com