Study links sleep apnoea to memory loss

UCLA researchers have, for the first time, discovered that people with sleep apnoea show tissue loss in brain regions that help store memory.

Sleep apnoea occurs when a blocked airway repeatedly halts the sleeper’s breathing, resulting in loud bursts of snoring and chronic daytime fatigue. Memory loss and difficulty focusing are also common complaints. Prior studies have linked the disorder to a higher risk of stroke, heart disease and diabetes.

The findings demonstrate that impaired breathing during sleep can lead to a serious brain injury that disrupts memory and thinking.

The scientists hypothesize that repeated drops in oxygen lead to the brain injury. During an apnoea episode, the brain’s blood vessels constrict, starving its tissue of oxygen and causing cellular death. The process also incites inflammation, which further damages the tissue.

Obstructive sleep apnoea occurs when the muscles in the throat, soft palate and tongue relax during sleep and sag, narrowing the airway. The tongue slides to the back of the mouth, blocking the windpipe and cutting off oxygen to the lungs. The sleeper wakes up, gasping for air, and falls back into a fitful sleep. The cycle can repeat itself hundreds of times per night.

The study focused on structures on the underside of the brain called mammillary bodies, so named because they resemble small breasts. The scientists discovered that the sleep apnoea patients’ mammillary bodies were nearly 20 percent smaller, particularly on the left side. The reduced size of the mammillary bodies suggests that they suffered a harmful event resulting in sizeable cell loss. The fact that patients’ memory problems continue despite treatment for their sleep disorder implies a long-lasting brain injury.

The findings are important because patients suffering memory loss from other syndromes, such as alcoholism or Alzheimer disease, also show shrunken mammillary bodies.

Physicians treat memory loss in alcoholic patients with massive amounts of thiamine, (vitamin B1) because they suspect that the dose helps dying cells to recover, enabling the brain to use them again.

In a future study, the scientists will explore whether taking supplemental vitamin B1 helps restore the memories of sleep apnoea patients. The vitamin helps move glucose into the cells, preventing their death from oxygen starvation.

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