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08-01-2012 | Psychology | Article

Night shift work linked to diabetes risk in women


Free abstract

MedWire News: Women who work rotating night shifts on a long-term basis are at an increased risk for developing Type 2 diabetes, a US study shows.

The research has potential public health significance due to the large proportion of the working population involved in some kind of permanent night and rotating night shift work, say Frank Hu (Harvard Medical School, Massachusetts, USA) and colleagues.

The researchers studied 69,269 participants from the Nurses' Health Study ([NHS] I, 1988-2008) and 107,915 participants from NHS II (1989-2007) who were initially free from diabetes and cardiovascular disease.

In both cohorts, questionnaires were administered at baseline to establish how long the women had worked rotating night shifts (defined as working at least 3 nights per month in addition to days and evenings).

The team then sent the participants biennial questionnaires to collect information on their lifestyle and incidence of chronic disease over a follow-up period of 18 to 20 years.

At baseline, 59.0% of all women in NHS I reported engaging in rotating night shift work for a year or more, with 11.3% reporting having done so for 10 years or more. The corresponding figures for NHS II were 61.9% and 4.4%.

During the follow-up period, 6165 and 3961 cases of incident diabetes were recorded in the NHS I and NHS II cohorts, respectively.

As reported in the journal PLoS Medicine, Cox proportional hazard modeling revealed a significant association between the duration of shift work and risk for Type 2 diabetes in both cohorts, after adjustment for diabetes risk factors.

Indeed, compared with women who had not engaged in any rotating night shift work, the pooled hazard ratios (HRs) for Type 2 diabetes in participants who had worked 1-2, 3-9, 10-19, and 20 years or more of rotating night shifts were 1.05, 1.20, 1.40, and 1.58, respectively.

After additional adjustment for change in body mass index, the association was attenuated but remained significant, at respective pooled HRs of 1.03, 1.06, 1.10, and 1.24, respectively.

The researchers say that rotating nightshift work is generally associated with disruption to sleep-wake cycles and chronic misalignment between the endogenous circadian timing system and the behavior cycles.

"This misalignment has previously been found to result in adverse metabolic and cardiovascular responses including a decrease in leptin, an increase in glucose and insulin, an increase in mean arterial blood pressure, and reduced sleep efficiency," they explain. "Furthermore, the increase in glucose seems to be the result of an exaggerated postprandial glucose response."

"Recognizing that rotating night shift workers are at a higher risk for Type 2 diabetes should prompt additional research into preventive strategies in this group," they conclude.

By Sally Robertson

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