Sleep Apnoea Linked To Memory And Thinking Decline

Researchers in the US have reported that sleep-disordered breathing, characterised by abnormal breathing patterns during sleep, may be associated with an earlier onset of memory and thinking problems in older people. The results are published on 15 April in the journal Neurology.

Sleep-disordered breathing (SDB) may affect around 20% of the general population and prevalence is reported to be higher in men and in older adults. It is characterised by changes in breathing patterns during sleep, which can range from heavy snoring to periods of sleep apnoea, where breathing completely stops for a short time. Around 4% of middle-aged men and 2% of middle-aged women in the UK are thought to have obstructive sleep apnoea, the most common form of the condition.

To investigate the effects of SDB on memory and thinking, researchers from NYU School of Medicine in New York and Rutgers School of Public Health in New Jersey analysed data from a group of 2,470 older people who were taking part in a long-term study called the Alzheimer’s Disease Neuroimaging Initiative (ADNI). This group had been tracked over time with cognitive tests and the researchers could see which participants had a type of SDB – those that reported themselves to have ‘sleep apnoea’ or ‘obstructive sleep apnoea’.

The researchers split the data into smaller groups, depending on the amount and quality of information they had available for each participant. Analyses of the data using the least stringent criteria showed that 63 out of 767 participants started the study with no memory and thinking problems and went onto develop MCI, whereas 217 already had a diagnosis of early memory problems called mild cognitive impairment (MCI).

The researchers found that those participants who reported sleep disordered breathing had a younger onset of MCI than those that did not report such sleep problems. The average age of onset was around 73 years in those with SDB compared to around 84 years in those without, and the magnitude of this difference remained when the researchers used more stringent criteria for their analysis. This effect also remained after the team adjusted their analysis to account for factors such as high body mass index and cardiovascular disease, which are also suggested risk factors for dementia and for sleep apnoea.

The researchers also looked at the age of onset of Alzheimer’s disease in the volunteers but did not see a difference for those with SDB over and above what could be expected by chance. A small number of participants had used a treatment method called continuous positive airway pressure (CPAP), which aims to normalise breathing during sleep. The researchers found that this treatment was associated with a delayed onset of memory problems in those with sleep-disordered breathing.

Dr Simon Ridley of Alzheimer’s Research UK, the UK’s leading dementia research charity, said:

“This study adds to evidence that disrupted breathing during sleep could be a risk factor for memory and thinking decline in older age, but it doesn’t prove that one causes the other. Despite the small sample size in this study, the researchers did try to account for other factors that may have explained the link and the findings highlight the need to delve deeper into the possible biological reasons behind this association. A good supply of oxygen to the brain is vital to keep it healthy and it is interesting to see that treatment of sleep apnoea was associated with a trend towards a later onset of memory and thinking problems.

“Sleep problems are very common, but it’s important to note that this study focused on sleep apnoea, which affects less than 5% of the population. While heavy snoring is a feature of sleep apnoea, not everyone who snores will have the condition. If people are worried they may have sleep apnoea, they should discuss this with their doctor as there are approaches available to help.”