The discovery of a causal link between a lack of oxygen to the brain during sleep in mice and Alzheimer’s disease has lessons for humans, researchers say.

Having developed a way to induce sleep-disrupted breathing in mice, researchers at The University of Queensland saw displays of “exacerbated pathological features of Alzheimer’s disease”.

“It demonstrated that hypoxia, when the brain is deprived of oxygen, caused the same selective degeneration of neurons that characteristically die in dementia,” Professor Elizabeth Coulson said.

The next step is to investigate what levels of hypoxia result in brain degeneration in humans.

It’s estimates that about half of all elderly people have obstructive sleep apnoea, when their throat muscles intermittently collapse and block the airway during sleep, Professor Coulson said.

The current gold standard for treatment is a continuous positive airway pressure (CPAP) machine, which keeps airways open during sleep.

“We couldn’t fit CPAP to mice, but we experimentally prevented the hypoxia and this stopped the cognitive impairment and neuron death, and also reduced the Alzheimer’s pathology,” Prof Coulson said.

“This suggests that CPAP treatment of obstructive sleep apnoea has the potential to reduce dementia risk.”

The findings could change the way dementia clinicians diagnose and treat their patients.

“Thirty per cent of people with obstructive sleep apnoea being fitted for CPAP machines already display signs of dementia-like cognitive impairment,” she said.

“Unfortunately the hospital system isn’t referring those people to dementia clinics.”

Not everyone with obstructive sleep apnoea will get dementia, but the at-risk population needs to be defined, Prof Coulson said.

“Early stage human trials are underway with sleep clinicians in Brisbane and Sydney to determine the correlation between hypoxia and sustained cognitive impairment, and whether CPAP can reduce dementia risk.”

Nick Gibbs
(Australian Associated Press)