A recent population study from the United Kingdom adds to the growing body of evidence showing associations between OSA and an increased risk of cognitive decline. Promisingly, however, the new data show early treatment with CPAP may reduce or eliminate that risk.

In the study, OSA was associated with a 12% increased risk for all-cause dementia and 29% increased risk for vascular dementia compared with propensity-matched individuals without OSA. Results were derived from 2.3 million adults across the United Kingdom from 2000 to 2022, including 193,600 adults with OSA.¹

This is the latest of multiple studies showing associations between cognitive decline and OSA or other measures of poor sleep quality and quantity, said Sreelatha Naik, MD, FCCP, Director of Pulmonary and Critical Care Medicine for Geisinger Health System Northeast Region and Chair of the CHEST Respiratory-Related Sleep Disorders Section. Multiple neurodegenerative dysfunctions, disorders, and syndromes have long been associated with disrupted sleep patterns.

“OSA is just one cause of poor sleep,” Dr. Naik said. “There’s also short sleep, when I decide I’m going to do an all-nighter, and, tomorrow, you can measure in my blood higher levels of tau protein, which is a neurotoxic protein. The most important strategy is prevention because it’s always better to prevent things than to treat them later.”

Minor cognitive dysfunction is the most often cited outcome from poor sleep, she added, but cognitive dysfunction covers a wide spectrum, from mild and transitory to disabling and progressive.

Disorders such as Alzheimer’s disease feature prominent cognitive decline. There is a larger group of α-synucleinopathies and tauopathies that includes not just Alzheimer’s disease but also Parkinson’s disease and related disorders, progressive supranuclear palsy, and more. All fall under the larger umbrella of neurodegenerative disorders and dementia.

“When I talk about these disorders with residents and fellows, I use a very technical term: brain poop,” Dr. Naik said. “These brain waste products—tau protein and α-synuclein—are not just brain poop, they are toxic brain poop that cause the death of neuronal cells and take out the nuclei in the brain that cause good sleep. Normally, when we sleep, we get rid of this toxic stuff, so poor sleep accelerates this pathology that attacks your sleep mechanism, which causes worsening sleep. You’re getting more sleep-deprived, which causes more neurodegeneration.”

The UK study was relatively short-term with a median follow-up of just four years. Of the 2.3 million adults studied, 2,802 without OSA and 6,211 with OSA developed dementia from any cause. Individuals with OSA who had received CPAP treatment showed a similar risk for all-cause dementia as matched counterparts who did not have OSA.

The apparent benefit of CPAP therapy is not a complete surprise, Dr. Naik said. Retrospective studies have found abnormal sleep patterns as long as 20 years before diagnosis in patients with Parkinson’s disease. There have been no long-term studies on the effect of CPAP or other sleep therapy on neurocognitive function later in life.

“We need more studies that show whether treating sleep apnea and truly meeting all the outcome parameters are ultimately going to improve, or at least mitigate, that effect of sleep apnea on dementia risk,” Dr. Naik said. “Now that we have this association, the real question is, if we treat sleep apnea now, is it going to change the dementia outcome down the road? And if it does not, what are the confounders we’re not addressing?”

1. Wang J, Subramanian A, Cockburn N, Xiao J, Nirantharakumar K, Haroon S. Obstructive sleep apnoea syndrome and future risk of dementia among individuals managed in UK general practice. Thorax. 2025;80(3):167-174. doi:10.1136/thorax-2024-221810