We all know that being overweight increases the chances of getting type 2 diabetes. But is there another culprit? New evidence suggests that the amount of sleep we get, and when we get it, is also linked to diabetes.
Diabetes is known as a metabolic disease, because the body does not metabolise food into energy properly. In the case of type 2 diabetes, people's bodies stop reacting properly to insulin, or don’t produce enough insulin. It’s the hormone insulin that helps the body to regulate the amount of sugar in the bloodstream. Cells around the body rely on sugar in the blood to get energy, but too much sugar in the bloodstream damages blood vessels and causes poor circulation and heart attacks, amongst other problems.
Being overweight is one of the most common causes of type 2 diabetes, although not everyone with diabetes is overweight.
Several large studies have looked at differences between people with diabetes and people without. As well as finding the expected link between being overweight and diabetes, many studies have also found that people with diabetes are more likely than those without the condition to have problems sleeping.
Dr Emily Burns, research communications manager at Diabetes UK, says: "The research that we have at the moment confirms there's a link between sleep and type 2 diabetes."
She pointed to a recent study of more than 230,000 people in the UK (part of the huge UK Biobank research project) that looked at sleep alongside other behaviours such as watching TV and physical exercise.
The study confirmed that people with type 2 diabetes - with or without cardiovascular disease - were likely to spend more time watching TV and less time doing physical exercise than people without diabetes. However, the study also found they were more likely to have an unhealthy sleep pattern - either sleeping more than 8 hours a night, or less than 7 hours.
The idea that the 'optimum' amount of sleep is between 7 and 8 hours has been around for a while. One recent summary of 10 research studies into sleep and diabetes found a 'U-shaped' relationship between sleep and risk of getting diabetes. People who had between 7 and 8 hours sleep a night had the lowest chance of getting type 2 diabetes, while people who slept for one hour longer or shorter had an increased risk of getting diabetes of between 9% and 14%.
However, the type of studies we're talking about here can't prove that lack of sleep causes diabetes. They can only show there's a link between diabetes and sleep. What researchers really want to know is why that is.
"The UK Biobank study authors mention in their conclusions that sleep deprivationis a prominent unaddressed risk factors in type 2 diabetes at the moment," says Dr Burns. "We've got so many epidemiological studies now, all pointing to that conclusion, but unless we understand why, we can't do anything about it. And we can't understand why, without a trial."
By a trial, she means a randomised controlled trial, where people at high risk of getting diabetes are divided randomly into two groups, one group told to sleep for one hour longer than the other, to see what difference that makes to their metabolism. "That's where the research community feel this should be going, what the next step should be."
Source: Boots Web April 2016