Is shift work a risk factor for type 2 diabetes?

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Type 2 diabetes rates are on the up, and there is real concern within the medical community that we are seeing something of a ‘diabesity’ epidemic that has considerable personal and social consequences. The usual focus regarding the prevention of type 2 diabetes is ‘diet and exercise’. But, other less well-recognised factors appear to influence diabetes risk, and one of these is sleep.

I was interested to see a recently published study which links shift work with an increased risk of type 2 diabetes, and this association was particularly strong in men [1]. This study cannot be used to conclude that shift work somehow causes diabetes (only that they are associated). The same is true of studies which have linked short-sleep with an increased risk of diabetes [2].

However, there is some evidence that short sleep has the potential to impair blood sugar control (glycaemic control).

In one study, nine healthy adults were tested to see what effect sleep deprivation has on insulin resistance [3]. On one night, individuals were allowed to sleep for up to 8.5 hours (23.00 – 7.30 hrs). On another night, sleep was only permitted for four hours (01.00 – 05.00 hrs). The actual average sleep times were 7 hours 34 minutes and 3 hours 46 minutes respectively.

The results showed that in the sleep-deprived state there was evidence of insulin resistance. ‘Endogenous’ sugar production (internal production of sugar, say, from the liver) was higher, and clearance of glucose (say, into muscle cells) was lower in the sleep-deprived state.

Now, less than four hours sleep is not much sleep. But then again, increased insulin resistance was seen in individuals after just one night of sleep deprivation. It’s possible that less extreme sleep deprivation or sleep disruption (such as shift work) over longer periods of time also poses hazards regarding diabetes risk.

In one study, the impact of ‘shift work’ on disease markers, including those for diabetes [4]. 26 healthy individuals were allowed to sleep for up to 10 hours a night for 10 nights. Then, they were restricted to no more than 5 hours sleep for 8 nights. In this setting, some individuals took their sleep at night. Others, however, simulated ‘shift work’ by taking their sleep in the day on four of the eight days.

Short sleep led to a reduction in insulin sensitivity (as has been noted in previous studies), as well as an increase in markers of inflammation. Also, in men, reductions in insulin sensitivity and increases in inflammation were about twice a bad when they were sleeping in the ‘shift’ setting, compared to those sleeping normally (at night).

The evidence as it stands supports the idea that both duration and pattern of sleep can have a bearing on risk of type 2 diabetes, and other chronic health issues too.


1. Gan Y, et al. Shift work and diabetes mellitus: a meta-analysis of observational studies Occup Environ Med doi:10.1136/oemed-2014-102150

2. Chaput JP, et al. Sleep duration as a risk factor for the development of type 2 diabetes or impaired glucose tolerance: Analyses of the Quebec Family Study. Sleep Med. 2009;10(8):919-24

3. Donga E, et al. A single night of partial sleep deprivation induces insulin resistance in multiple metabolic pathways in healthy subjects. J Clin Endocrinol Metab. 2010;95(6):2963-8

4. Leproult R, et al., Circadian misalignment augments markers of insulin resistance and inflammation, independently of sleep loss. Diabetes. 2014;63(6):1860-9

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