There is a complicated yet established relationship between cognitive decline and sleep apnea. It has been found that quality sleep helps to clear the brain of excess fibers that may otherwise turn into plaques (which are a known marker of Alzheimer’s disease). However, large-scale studies including individuals with sleep apnea have shown mixed results, and findings show those with sleep apnea do not perform worse on cognitive testing than those without sleep apnea. So what gives? Does sleep apnea not actually contribute to cognitive decline? A group of researchers at New York University recently asked a different question: does sleep apnea initiate cognitive decline earlier than it would ordinarily occur?
This question was investigated using a large group of individuals known as the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort. This longitudinal cohort includes participant demographics, sleep apnea status, apnea treatment status, and outcome descriptions of whether these individuals declined to Alzheimer’s disease or to the precursor of Alzheimer’s, referred to as Mild Cognitive Impairment (MCI). Cognitive outcomes were compared between those with untreated sleep apnea and those without sleep apnea. They were also compared between those with untreated and treated sleep apnea. This comparison was used to see whether treating sleep apnea would work to “cancel out” damage caused by apneas.
It was found that those with untreated sleep apnea experienced cognitive decline around 72 years of age, while those without sleep apnea experienced it around 84 years of age. Amazingly, though, it seems that sleep apnea treatment is able to delay the onset of cognitive decline. Treated individuals experienced cognitive decline around 82, rather than 72, which brings them almost to the ‘normal’ age for experiencing cognitive decline.
Out of everything we have discussed here, this might be the most important. This study suggests cognitive decline occurs about 10 years earlier for those who have untreated sleep apnea than those without sleep apnea. Importantly, though, apnea treatment reverses this trend, and treated individuals do not experience cognitive decline earlier than those without sleep apnea. If you need another reason to stick to your apnea treatment, look no further – stay treated to keep your cognitive health intact.
Source: Osorio, R. S., Gumb, T., Pirraglia, E., Varga, A. W., Lu, S. E., Lim, J., & Alzheimer's Disease Neuroimaging Initiative. (2015). Sleep-disordered breathing advances cognitive decline in the elderly. Neurology, 10-1212.