Untreated Sleep Apnea Linked to 69% Faster Cognitive Decline Over 10 Years

This is an observational study in people, not a trial. The researchers, led by Kaufmann and Spira, analyzed 777 participants in the National Health and Aging Trends Study, a nationally representative study of Medicare beneficiaries aged 65 and older. Each had at least one Medicare claim for obstructive sleep apnea and no sign of dementia at the start in 2011. A study like this can show a link. It cannot show that one thing caused the other.

Obstructive sleep apnea is a condition in which the throat repeatedly collapses during sleep. According to the paper, nearly one billion people worldwide have it. It raises the risk of heart disease and early death. Continuous positive airway pressure, or CPAP, is the first-line treatment recommended by the American Academy of Sleep Medicine. A CPAP machine delivers a steady stream of air to keep the airway open. The authors note that many people with sleep apnea remain untreated.

Cognition was assessed each year from 2011 to 2021. The score combined word recall tests, questions about the date and day of the week, and naming the President and Vice President. Thinking performance declined in the group as a whole. Participants with a CPAP claim declined by 0.03 standard deviation units per year (95% confidence interval: −0.04 to −0.02). Untreated participants declined 69% faster (CPAP-by-time interaction: −0.02; 95% confidence interval: −0.04 to −0.001). The upper end of that range sits very close to zero, so the size of the gap is uncertain.

The finding speaks to a puzzle. Large studies have linked CPAP use to lower dementia risk. Shorter trials have found little cognitive benefit. One of them, the APPLES trial of more than 1,000 people with moderate to severe sleep apnea, found only small improvements at 6 months. The authors argue that cognitive decline unfolds over many years, so short follow-up may miss it. Their 10-year data point in that direction.

There are important limits. CPAP use was defined by one or more device claims at any time between 2008 and 2021, and treated as fixed for the whole study. Claims show that a device was billed, not whether anyone used it each night. People who get CPAP may also differ in other ways from those who do not. The researchers considered factors including age, sex, education, body weight, heart disease, diabetes, depression and smoking, and adjusted for those linked to CPAP use, but adjustment cannot remove every difference. The authors' own conclusion is cautious: CPAP therapy "may slow cognitive decline in older adults with OSA."

The Arising's October 9 report on a gut bacteria molecule linked to Alzheimer's protein buildup was a different study on a different possible risk factor. This one adds a separate line of research on factors that might be changed.

The authors call for studies of how treatment might prevent cognitive decline, and for long-term studies that link data recorded by treatment devices to medical claims, to show how adherence and intensity of use relate to brain health.

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