The study, led by the University of Bristol, supported by the universities of Manchester, Exeter, and Harvard, and funded by Diabetes UK, is published in Diabetes Care.
Insomnia, not getting enough sleep, and having a later bedtime, have been linked in previous studies to a greater risk of type 2 diabetes. In this study, the research team assessed whether these associations are explained by causal effects of sleep traits on blood sugar levels
The researchers used a statistical technique called Mendelian Randomization to see how five sleep measures - insomnia, sleep duration, daytime sleepiness, napping and morning or evening preference (chronotype) - were related to average blood sugar levels assessed by a measure called HbA1c levels. Using Mendelian Randomization, which groups people according to a genetic code randomly assigned at birth, allowed the researchers to remove any bias from the results.
The study of over 336,999 adults living in the UK, showed that people who reported that they often had difficulty getting to sleep or staying asleep had higher blood sugar levels than people who said they never, rarely, or only sometimes had these difficulties. The research team found no clear evidence of an effect of other sleep traits on blood sugar levels.
The findings could improve researchers' understanding of how sleep disturbance influences type 2 diabetes risk. The study also suggests that lifestyle and/or pharmacological interventions that improve insomnia might help to prevent or treat diabetes.