Sleep apnoea may contribute to dementia by starving brain of oxygen at night, suggests study

Oxygen deprivation caused by a common sleep complaint could cause your brain to shrink in the regions which play an important role in memory and which are also affected by dementia, Australian researchers have found.

A new study shows that people with obstructive sleep apnoea (OSA) had a reduced thickness in their temporal lobes, and performed more poorly on memory tests.

Now the team from the University of Sydney say screening for the condition could help to stave off this memory deterioration by offering treatment that supports the airways while they sleep.

“Our results suggest that we should be screening for OSA in older people,” said Professor Sharon Naismith who led the research team. “We should also be asking older patients attending sleep clinics about their memory and thinking skills, and carrying out tests where necessary."

Obstructive sleep apnoea is a condition where the throat relaxes and narrows during sleep to the point that it cuts off breathing.

The condition becomes more common in old age, and in people who are overweight, and makes high blood pressure, diabetes and sleep disruption more likely – which are all factors associated with dementia.

For the research, published in the European Respiratory Journal , they recruited 83 people between the age of 51 and 88 who had seen their doctor with memory or mood concerns which could be an early sign of dementia. None of the participants had a diagnosis of OSA.

They were each given memory tests and MRI scans to assess their brain thickness, and attended a sleep clinic while their blood oxygen levels were measured overnight.

It found that people with a lower blood oxygen level, suggesting they were not breathing properly at night, had shrinking in the left and right temporal lobes and were less able to retain new information in the memory tests – the first time such a link has been shown.

Researchers also saw an increased thickness in other regions of the brain which may be a sign of oxygen-deprivation-linked inflammation and swelling.

Prof Naismith’s team is now looking at whether treating people in this at risk group by treating their OSA with a CPAP machine - a ventilator and mask which gently pushes air into the lungs to keep the airways open.

"There is no cure for dementia so early intervention is key,” she said. “On the other hand, we do have an effective treatment for OSA. This research shows that diagnosing and treating OSA could be an opportunity to prevent cognitive decline before it's too late."

As much as 50 per cent of a person’s dementia risk is thought to be due to preventable lifestyle factors like smoking, obesity and high blood pressure and sleep disturbance is an increasingly studied issue.

“This adds to evidence that OSA is also linked to dementia and suggests a likely mechanism for the link,” said Professor Andrea Aliverti, professor of bioengineering at Politecnico di Milano, Italy of the findings, which he was not involved with.