New analysis confirms connection between shift work and type 2 diabetes

by Barbara Hewitt on August 28, 2014

A new analysis of existing studies confirms a link between working night shifts and developing type 2 diabetes, but scientists say more work is needed to find out why.

People who work night shifts, or constantly changing shifts, are more likely to develop type 2 diabetes compared to non-shift workers, with men on rotating shifts being the most vulnerable, says the work done by researchers at Tongji Medical College in China.

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Scientists combined data from twelve separate studies worldwide

But the reasons why men working a particular shift pattern are more at risk are unclear, according to the analysis, led by Zuxun Lu, which re-analysed data from 12 previous studies that looked at the association between shift work and chances of developing diabetes.

The studies included a total of 226,652 participants and 14,595 people with diabetes and were published between 1983 and 2013. Six of the studies were conducted in Japan, two each from the United States and Sweden and one each from Belgium and China.

Shift work includes working nights, evenings, rotating shifts or irregular shifts; in fact, anything other than working typical daytime hours. The study authors said that based on their analysis, the risk of diabetes was increased by 9% overall for shift workers compared to people who had never been exposed to shift work.

Male shift workers had a 28% greater risk of developing diabetes than their female counterparts. And people who worked rotating shifts had a 42% greater risk of diabetes compared to non-shift workers.

Lu pointed out that it is not known how long the participants in those studies had been shift workers, which limits the ability to interpret their results. The new analysis also doesn’t prove that shift work causes diabetes or explain how it might do so.

‘More prospective cohort studies with long follow-up periods are warranted to replicate our findings and reveal the underlying biological mechanism,’ said Lu, adding that shift work may interfere with eating and sleeping patterns and disrupt circadian rhythms.

‘Some studies have shown that insufficient sleep and poor sleep quality may develop and exacerbate insulin resistance,’ he explained.

Previous studies show that shift work is associated with weight gain and an increase in appetite and body fat, which are major risk factors for diabetes.

Currently, there is fairly convincing evidence that there is an association between a misalignment of circadian rhythm and risk for diabetes, according to  Dr. Peter Butler, director of the Larry L. Hillblom Islet Research Center at the David Geffen School of Medicine at the University of California, Los Angeles.

But he pointed out that shift working is not a problem for most people and that most people on night shifts don’t get diabetes. ‘Probably about 20% of us are vulnerable to diabetes, and what I think probably happens is the people who get diabetes in relation to shift work are the ones who were vulnerable to getting diabetes anyway,’ he explained.

He said avoiding rotating shifts might be a good idea for people who have a strong family history of diabetes. But people who are at risk and have to work rotating shifts can still reduce the likelihood that they’ll get diabetes. ‘You can counter the risks for diabetes by regular exercise and good diet,’ he added.


The opinions expressed in this article do not necessarily reflect the views of the DiabetesForum.com Community and should not be interpreted as medical advice. Please see your doctor before making any changes to your diabetes management plan.

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