Getting less than six hours sleep each night (compared to seven hours) may increase type 2 diabetes risk by 30 per cent but has less impact on heart disease than previously thought, researchers from the University of Newcastle have found.
In the largest study of its kind, the team led by Hunter Medical Research Institute statistician Dr Elizabeth Holliday and epidemiologist Professor John Attia analysed data from 240,000 people in the NSW 45 and Up study and tested for potential contributing factors such as existing illnesses and medications.
“A number of previous studies have looked at sleep deprivation and the risk of both diabetes and cardiovascular disease but the statistical power was relatively low and not all of them had corrected for potential confounders that can affect results,” Professor Attia said.
“Once we adjusted for the confounders the risk for heart disease went away, other than in those who had prior illness, but the relationship with type 2 diabetes remained significant no matter what we adjusted for.”
Of the 240,000-strong cohort, more than 7,000 people fell into the risk category of fewer than six hours’ sleep, with the findings just published in the international journal Plos One.
Dr Holliday said it was surprising to see the cardiac link diminish.
“The relationship between short sleep and cardiovascular disease has been widely reported but results across various studies have been inconsistent. We were able to show that this relationship might be confounded by pre-existing illness, which we didn’t see with diabetes,” she said.
The researchers believe the results tie in with previous studies where volunteers became insulin resistant after several consecutive nights of acute sleep deprivation.
“There are other changes in hormones such as ghrelin and leptin that regulate hunger and the feeling of satisfaction after eating,” Dr Holliday added. “When you’re sleep deprived you tend to crave carbohydrates and eat more sweets.”
Tips to improve sleep quality include exercising before 6pm, abstaining from caffeine in the afternoon and early evening, reducing stimulation from social media and texts, and observing regular bed and rising times.
“GPs should be interested in this result because there are a number of people with pre-diabetes who are at high risk,” Professor Attia said. “Getting more sleep might be a way of improving insulin sensitivity and delaying the onset of frank diabetes.
“It may also be a factor for people who are already diabetic and having trouble getting glucose control.”
HMRI is a partnership between the University of Newcastle, Hunter New England Health and the community.