People with restless legs syndrome had roughly twice the risk of later Parkinson's disease. People with sleep apnea had a raised risk of vascular brain disease.
Both patterns come from a large 2026 analysis published in Alzheimer's & Dementia, led by Kim and colleagues. The researchers drew on the UK Biobank, comparing about 30,000 middle-aged and older adults with diagnosed sleep disorders against roughly 147,000 without.
Overall, having any sleep disorder was tied to a 32 percent higher risk of developing a neurodegenerative disease. Restless legs syndrome produced the strongest single signal in the analysis, with a hazard ratio of 2.01 for Parkinson's disease.
Sleep apnea was tied to a 49 percent higher risk of vascular neurodegenerative disease and a 37 percent higher risk of Parkinson's.
Also read: Your calcium and vitamin D supplements may not be protecting your bones at all
Why the sleep problem often comes first
Restless legs syndrome is a nervous system condition that produces an uncomfortable urge to move the legs, usually when the person is sitting still or trying to fall asleep. The proposed link to Parkinson's runs through iron and dopamine.
Reviews of the two conditions describe shared disturbances in brain iron and dopamine signaling, and low iron in specific brain regions can impair the same dopamine pathways that fail in Parkinson's. That may be why restless legs sometimes shows up years before a Parkinson's diagnosis.
Sleep apnea, in which breathing repeatedly stops during sleep, appears to injure the brain through a different route. Repeated dips in blood oxygen fuel oxidative stress and small-vessel disease, which fits the pattern that apnea tracks most strongly with vascular brain disease rather than pure Parkinson's.
Both conditions are widespread in the US
Restless legs syndrome affects roughly 5 to 10 percent of US adults, according to the National Institute of Neurological Disorders and Stroke.
Also read: For depression and anxiety, one type of exercise consistently outperforms the rest
Obstructive sleep apnea is even more common. A 2025 systematic review in Respiratory Medicine estimated 83.7 million American adults, or 32.4 percent, were living with OSA in 2024, and the authors noted that most cases go undiagnosed.
What it means for readers
The Kim analysis is observational and cannot prove that treating a sleep disorder prevents brain disease. But the authors argue that sleep symptoms often surface years before any clinical neurological diagnosis, which points to these disorders as potential early markers rather than downstream effects.
Both conditions are treatable. Restless legs symptoms often improve with iron replacement, lifestyle changes and, if needed, medications such as gabapentin or dopamine agonists. Sleep apnea responds to weight loss and continuous positive airway pressure (CPAP) therapy.
Anyone bothered by an urge to move the legs at night, loud snoring, gasping in sleep or heavy daytime sleepiness should raise it with their doctor. The new evidence suggests the payoff of treating these conditions may reach further into future brain health than previously understood.
Also read: Too little sleep rivaled smoking as a predictor of how long people live
Also read: The nutrients your aging eyes need most - and the foods that deliver them