New theory as to why some people die during sleep

According to scientists the reason why some people stop breathing fatally in their sleep, is because a cumulative loss of cells in the area of the brain that controls breathing triggers a condition called central sleep apnoea.

Sleep apnoea is a condition which usually jolts people awake.

They scientists say they believe many such deaths in elderly people are misdiagnosed as heart failure.

Researchers at the University of California, Los Angeles (UCLA) , had already pinpointed a region of the brainstem they dubbed the preBötzinger complex (preBötC) as the command post for generating breathing in mammals, and a small group of cells within this area, as being responsible for issuing the commands.

In their latest study, they injected rats with a compound to kill more than half of these cells, and then monitored the animals' breathing patterns.

They found that when the animals entered the rapid eye movement phase of sleep, when dreaming occurs, they stopped breathing completely, and were jolted into consciousness in order to start again.

Over a period of time, the breathing lapses increased in severity, spreading to other phases of sleep, and eventually occurring when the animals were awake as well.

Apparently rats possess 600 of these specialised cells, and the researchers believe humans have a few thousand, which are slowly lost over a lifetime.

Professor Jack Feldman, the lead researcher, suggests that our brains can compensate for up to a 60% loss of preBötC cells, but the cumulative deficit of these brain cells eventually disrupts our breathing during sleep.

He says as there is no biological reason for the body to maintain these cells beyond the average lifespan, so they are not replenished as we age, and as we lose them, we grow more prone to central sleep apnoea.

The team at UCLA believe that central sleep apnoea may present a risk in particular to elderly people, whose heart and lungs are already weaker due to age.

They also have suspicions that the condition strikes people suffering the late stages of neurodegenerative disorders, such as Parkinson's disease.

Such people often have breathing difficulties during sleep, and the researchers believe their bodies eventually reach a point where they are unable to rouse themselves from sleep when they stop breathing.

The next step for the UCLA team is to analyse the brains of people who die from neurodegenerative diseases to determine whether these patients show damage in their preBötzinger complexes.

Previous studies have linked cot death to obstructive sleep apnoea, caused by collapse of the airways.

But science as yet has failed to definitively prove that link, and some now wonder if cot deaths may instead be linked to central sleep apnoea.

The study is published in Nature Neuroscience.