BREATHING difficulties during sleep may be an early warning sign of future Alzheimer's disease, researchers believe.
Experts are not sure how sleep-disordered breathing (SDB) and Alzheimer's are linked but evidence suggests some people who suffer from the sleep problem may already be starting to develop pre-symptomatic dementia.
SDB is an umbrella term for a group of conditions that affect breathing during sleep.
The most common is obstructive sleep apnoea – resulting in repeatedly interrupted breathing during sleep and is often accompanied by heavy snoring.
Study leader, Dr Ricardo Osorio from New York University School of Medicine, said: "We know that about 10 to 20pc of middle-aged adults in the US have SDB, that number jumps dramatically in those over the age of 65.
"One factor may be that some of these patients are in the earliest pre-clinical stages of AD (Alzheimer's disease)."
A group of 68 men and women with an average age of 71 and no evidence of dementia took part in the study.
Around half (48.5pc) were found to have mild SDB and a quarter had moderate-to-severe SDB. Alzheimer's biomarkers were only found among lean participants with SDB. In these patients, a progressive association was seen between the severity of SDB and the level of two indicators based on proteins and brain scans.
The findings were presented at the American Thoracic Society 2013 annual conference in Philadelphia.
Dr Osorio said it was not clear which condition came first, SDB or Alzheimer's, adding: "Our study didn't determine the direction of causality, and, didn't uncover a significant association between the two, until we broke out the data on lean and obese patients."
His team plans to test a theory that brain damage caused by very early stage Alzheimer's can trigger SDB in lean individuals who would otherwise not be affected. Obesity is a risk factor for breathing problems during sleep.