Working shifts 'elevates diabetes risk'

25 July 2014

People who work shifts have a far higher risk of developing type 2 diabetes, with the risk highest among men and those working rotating shift patterns, according to new research published in the journal Occupational & Environmental Medicine.

Previously, research has suggested links between working shifts and a heightened risk of various health problems, including digestive disorders, certain cancers, and cardiovascular disease, but it has not yet been clear whether diabetes can be added to the list.

As such, the authors have looked through scientific research databases, in a bid for relevant observational studies assessing associations between shift work and diabetes risk.

In total, they retrieved 12 international studies out of a potential total of 448, involving more than 226,500 participants, 14,600 of whom had diabetes.

When they compiled their results, the experts calculated that any period of shift work was associated with a nine per cent increased risk of developing diabetes, compared with working normal office hours.

This risk rose greatly for men - to 37 per cent - after further analysis examined the potential effects of factors such as gender, study design, study location, job, shift schedule, body mass index (BMI), family history of diabetes and physical activity levels.

According to the authors, men working shift patterns may need to pay more attention to the possible health consequences of their working schedule.

This is because daytime levels of the male hormone testosterone are controlled by the internal body clock, so it is possible that repeated disruption may affect this - something evidenced by research implicating low male hormone levels in insulin resistance and diabetes.

The majority of shift patterns, except mixed and evening shifts, were associated with a heightened risk of the disease compared with those working normal office hours, while rotating shifts, in which people work different parts of the 24-hour cycle on a regular basis, were associated with the highest risk of all, at 42 per cent.

A reason for this is that rotating shifts make it harder for people to adjust to a regular sleep-wake cycle, and some studies have suggested that a lack of sleep, or poor quality sleep, may prompt or worsen insulin resistance.

Other research has linked shift work to weight gain and increased appetite, both of which are risk factors for diabetes, while shift work may also disturb cholesterol levels and blood pressure, the researchers add.

A key point made by the authors was that, although their study was large, it was observational, so no conclusions can be drawn about direct cause and effect at the moment.

Despite this, they noted that any potentially modifiable factors could be of considerable public health importance, and are worth investigating further, given that an estimated 380 million people across the world will have type 2 diabetes by 2025.

Posted by Edward Bartel


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