Women who work irregular patterns swapping between day and night shifts could be at a higher risk of developing type 2 diabetes, according to research.
A study which focused on nurses in the US showed a link between periodic night shifts and incidence of type 2 diabetes diagnosis.
Nearly 178,000 women were studied across two decades as part of the long-running Nurse’s Health Study, all of whom were aged between 42 and 67.
The nurses who had worked night shifts over 20 years had a 58 per cent increased risk of developing type 2 diabetes compared to those who only worked in the day.
For nurses who only worked a three-year night shift stint, the risk was increased by 20 per cent.
Lead author Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health in Bosto, said: “The increased risk is substantial and can have important public health implications.”
The US research team thinks disrupted sleeping and eating patterns that working at night brings can lead to weight gain, increasing the risk of type 2 diabetes. Changing the body’s natural body clock can also upset healthy blood sugar levels and energy balance.
Previous research has suggested that lack of sleep or disrupted cycles of sleep can lead to insulin resistance and higher blood sugar, which are both indicators of diabetes.
During the study those who worked at least three nights a month, as well as day shifts, were considered to be a night worker.
The increased risk of type 2 diabetes ranged from five per cent for up to two years of working at night to 58 per cent across 20 years.
When the participants’ body mass index (BMI) was taken into account, the risk dropped to three per cent and 24 per cent, respectively, in these two groups.
Professor Hu said: “The overall risk associated with rotating shift work is probably due to the combination of biological factors resulting from disruption of circadian rhythms and … behavioral risk factors.”
The findings, which were largely based on white female nurses, have been published in the journal PLoS Medicine.

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