6 minute read
Sleeping On It
By Myke Bartlett
There’s a strong link between sleep apnoea and type 2 diabetes, although experts are divided on exactly how that link works. But can improving sleep have a real benefit for people with diabetes?
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We all know the difference a good night's sleep can make. When we sleep well, everything seems easier, whether it’s work, parenting or just putting up with other people. But new research suggests that the benefits of sleeping soundly extend far beyond improved mental health and wellbeing, particularly for those with chronic health conditions such as diabetes.
The study of sleep is a relatively new area in science, but extensive research exists around one of the most prevalent sleep disorders – sleep apnoea. Obstructive sleep apnoea (OSA) is a disorder in which, during sleep, breathing is interrupted by a blockage of the air flow, leading the body to wake itself up. Symptoms include snoring (which is also often associated with diabetes) and excessive, unexplained sleepiness during the day. There’s also a strong link between OSA, obesity and diabetes. People with OSA are more likely to develop type 2 diabetes and more than half of people with type 2 diabetes experience OSA. Untreated, both conditions can lead to cardiovascular disease.
Professor Danny Eckert
Professor Danny Eckert is leading research in sleep apnoea at Flinders University in Adelaide. He says that, like type 2 diabetes, sleep apnoea threatens to be a silent epidemic in Australia. “It’s estimated more than a million adult Australians have OSA and less than 10% are formally diagnosed,” Eckert says. “There’s a huge burden of disease out there that is untreated and, of course, that feeds into other chronic health conditions like diabetes.”
Sleep disorders are on the rise across the world, as we struggle to adapt to a pace of life that our bodies simply weren’t built for. Some 17% of Australians are shift workers and many are spending increasingly long times commuting for work. “Today’s 24 hour society puts a lot of pressure on us,” Eckert says. “Humans like regular sleep patterns and shift work poses a challenge to that. So does commuting. It all cuts into sleep time. The devices we’re all so linked to emit blue light, which suppresses hormones that help us get off to sleep.” These lifestyle issues also have strong links with obesity, which is a major risk factor for OSA. Around four out of 10 Australians are estimated to have poor sleep and, as with type 2 diabetes, those from lower socio-economic backgrounds or disadvantaged communities are at the greatest risk of sleep disturbance and obesity. But obesity alone doesn’t explain the strong comorbidity between OSA and type 2 diabetes. According to Professor Jonathan Shaw, pinning down the causal link has been far from straightforward. The assumption was that OSA had direct and broad-ranging impacts on the metabolism, Shaw says. “The two major parts of it are hypoxia (oxygen starvation) and arousal — as your body realises you’re in trouble, it wakes itself up and that rush of adrenaline is potentially harmful. It’s reasonably well established that’s one of the mechanisms by which OSA can affect blood pressure.” Given his extensive expertise and research in the area of diabetes, Shaw was keen to discover if treating OSA would have benefits for those living with diabetes. Despite promising results from other studies, the trial he oversaw failed to establish any concrete benefit. “OSA has been associated with poor blood glucose control, but when we tried improving sleep apnoea to see if it improved blood glucose control, it didn’t,” Shaw says. “Treating people's OSA didn’t make any difference to the control of their diabetes. For people who were sleepy, it made them less sleepy. For those without symptoms, it didn’t make any difference.” This doesn’t mean a causal link doesn’t exist between the two conditions. Shaw says it’s possible that the causal effect runs in the other direction, so that high blood sugars have a detrimental effect on sleep but it’s also possible that both conditions
Professor Jonathan Shaw
have some other underlying cause — perhaps psychological, neurological, biochemical, or autonomic. “These conditions are all connected, but not necessarily in the causal pathway we initially thought,” Shaw says. “Diabetes is associated with anxiety and depression, which in themselves bring about sleep disturbance. If you have hyperglycaemia and you’re having to get up three times a night to go to the toilet, that disturbs your sleep. There are a range of sleep disorders that are more common in people with diabetes. But almost everything is more common in people with diabetes.” While the treatment for sleep apnoea can be life changing for some, many find the continuous positive airway pressure (CPAP) device – essentially a mini ventilator – cumbersome and difficult to use, meaning any benefits must be seen to outweigh that difficulty. Shaw says a lack of conclusive evidence about those benefits for people with diabetes means people shouldn’t be rushing to get tested for OSA, particularly if they are not troubled by any debilitating symptoms. “It’s not an easy test to do, you’ve got to do some overnight trials,” Shaw says. “And then what do you do with the results? You’ve either got to lose some weight, which is the treatment we’d suggest for diabetes, or we’d be trying to suggest something like CPAP. But if you’ve got no symptoms, what are you going to get out of that? It’s not going to improve your diabetes, we tested that. If you don’t have symptoms, you’re not getting any benefit.” Eckert is reluctant to rule out any benefits for people with diabetes, however, even if the causal mechanism with OSA is unproven. “The evidence in terms of whether it affects your blood glucose control is a little mixed,” Eckert says. “The reason why that might be is that it turns out 50% of the people prescribed CPAP therapy can’t tolerate it. If you do a test in laboratory conditions and carefully monitor them wearing the CPAP for a week or so things do improve. If you can use it properly for a long period of time, it does help. In the real world, people only use it for a few hours a night or don’t use it often enough.” New, less intrusive therapies for sleep apnoea, including drug therapies, are likely to be better tolerated and increase benefits for people with OSA and diabetes. Anything that improves sleep is likely to bring some benefits. Eckert points to studies that show a definite link between poor sleep and poor blood glucose management. “If you take a healthy 20-year-old and you restrict their sleep to five hours a night for five nights in a row and you measure their blood glucose level, it’s as though they’re in a prediabetic state,” Eckert says. “That’s just five nights of sleep restrictions, but it’s a profound effect. There are also very strong links between sleep apnoea and a lack of glucose control. Getting a good night’s sleep will help.”
