Why Night Shift Workers Face Diabetes Risk

A new study may explain why nightshift works have a higher risk of type 2 diabetes.

The key may be melatonin, the hormone that helps regulate circadian rhythms.

In 2009, a team of Swedish researchers identified a common gene variant of the melatonin receptor 1B and determined that it raises the risk of type 2 diabetes by making it more sensitive to melatonin and impairing their ability to secrete insulin.

To better understand the effect of this gene on insulin secretion, the same researchers compared insulin secretion and glucose between 23 healthy people who had a gene variant of the melatonin receptor 1B and 22 healthy people who did not. All participants, who were matched for age, family history of diabetes, and body-mass index, took 4 mg of melatonin at bedtime every night for three months.

At the end of the trial, they observed that insulin secretion was significantly lower among people who had the gene variant. In addition, all participants had higher blood glucose levels after taking melatonin, but the increase was greater among those with the gene variant.

About a third of the population carries this gene variant and the study results show melatonin affects them more strongly, explained lead author Hindrik Mulder, PhD, a consultant at Skåne University Hospital and professor at Lund University in Sweden. “We believe that this explains their increased risk of developing type 2 diabetes,” he added.

The fact that the culprit in question is melatonin may shed light on the higher risk of type 2 diabetes among overnight workers and people with sleep disorders. Melatonin is sensitive to light. To maintain normal circadian rhythms, levels of the hormone increase overnight when it is dark, and decrease in daylight.

Based on these findings, published online on May 12 in Cell Metabolism, Mulder suggests further research into whether working overnight shifts could be more detrimental to people who carry this gene variant.