Black Women Working the Night Shift More Likely to Develop Diabetes

BEDFORD, MA – African-American women who work night shifts are significantly more likely to develop diabetes, and their risk increases the longer they work that schedule.

That’s according to a new study published in Diabetolgia, which notes that the increased risk is even greater in younger women.1

Varsha Vimalananda, MD, of the Center for Health Organization and Implementation Research (CHOIR), Edith Nourse Rogers Memorial VAMC in Bedford, MA, and colleagues at Boston University used data from a large ongoing study into the health of African-American women to reach that conclusion.

Background information in the article notes that previous studies have investigated the link between night shift work and diabetes, with links shown in both the Nurses’ Health Study (NHS), involving mostly white nurses in the United States, and a Swedish study. In those studies, however, body mass index was a key factor.

Given the increased prevalence of diabetes in black women in the U.S. of 12.6% compared to 4.5% in white women, the authors decided to investigate further in a population of black women.

Slightly more than 28,000 diabetes-free participants provided information in 2005 as part of the Black Women’s Health Study (BWHS) about having worked the night shift, according to the report. The women were tracked over the next eight years, with 1,786 incident diabetes cases reported.

Compared to never having worked the night shift, the increased risk of developing diabetes was 17% for one to two years of night shift work; 23% for three to nine years, and 42% for 10 or more years. After adjustment for BMI and lifestyle factors such as diet and smoking status, the association between increasing years of night shift work and increasing diabetes risk remained statistically significant, with a 23% increase in those who had worked night shifts for 10 years or more vs. those who never had worked the night shift.

Black women who ever had worked the night shift were at a 12% increased risk after adjustment for BMI and lifestyle factors, the authors found.

Interestingly, the association was stronger in younger women than in older women. Women younger than 50 who worked night shifts for 10 or more years had a 39% higher risk of diabetes compared to those who never had worked that schedule; the similar risk for women 50 or older was 17%.

“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,” the authors explain. “Shift work is associated with disrupted circadian rhythms and reduced total duration of sleep. Similar to the effects of jet lag, which are short term, shift workers experience fatigue, sleepiness during scheduled awake periods and poor sleep during scheduled sleep periods. These alterations in the normal sleep-wake cycle have profound effects on metabolism.”

The study suggested that the exact mechanisms behind the changes are not fully understood but note that, in animal models, circadian disruption affects beta cells which can decrease glucose-stimulated insulin secretion and trigger diabetes.

“In view of the high prevalence of shift work among workers in the USA — 35% among non-Hispanic blacks and 28% in non-Hispanic whites — an increased diabetes risk among this group has important public health implications,” the authors pointed out. “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.”

1 Vimalananda VG, Palmer JR, Gerlovin H, Wise LA, Rosenzweig JL, Rosenberg L, Ruiz Narváez EA. Night-shift work and incident diabetes among African-American women. Diabetologia. 2015 Jan 14. [Epub ahead of print] PubMed PMID: 25586362.


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