A recent study, titled, “Night-shift work and incident diabetes among African-American women,” published in Diabetologia by Dr. Varsha Vimalanda and colleagues in Boston shows a positive association between night shift work and type 2 diabetes among African-American women. The data now obtained by the Black Women’s Health Study (BWHS) confirms previous diabetes research on both white nurses in the USA and Swedish women.
Diabetes, which results from the abnormal regulation of blood glucose levels, is two times more prevalent in black women compared with white women in USA. Between 2005 and 2013, the BWHS followed 28,041 black non-diabetic women. Even after adjusting for body-mass index (BMI) and lifestyle, those that had worked night shifts before 2005 had a 12% higher risk of developing diabetes in comparison to those who had never worked night shifts. The association between night shifts and diabetes is stronger in younger women (<50 years) than in women aged 50 years or over (39% versus 17%). Importantly, the risk of disease also highly increases with the number of years working night shifts: 17% for 1-2 years night shift work to 42% for 10 or more years.
The authors of this study suggested that alterations in the sleep-wake cycle may explain the higher risk of diabetes: “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.”
Changes in sleep-wake cycle reflect a disruption of circadian rhythms, or biological clock, which also regulates metabolic pathways involved in diabetes. The detailed mechanisms are still unknown but beta cells that produce insulin in response to blood glucose seem affected by circadian variations. As reported by the authors: “In animal models, circadian disruption in susceptible rats led to more rapid loss of beta cell function and increased beta cell death, resulting in decreased beta cell mass, decreased glucose-stimulated insulin secretion and accelerated development of diabetes”
Since shift work is frequent among workers in the USA (35% among non-Hispanic blacks and 28% in non-Hispanic whites), these findings may have important implications in public health policies. The authors concluded: “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.”