Sleeping more than two hours with one’s head lying face upward (i.e., in supine position) was a significant nocturnal marker that characterized those with memory impairment, after controlling for factors such as age, sex, snoring, obstructive sleep apnea, and movements during the night.
– Daniel J. Levendowski, the study’s first author and President of Advanced Brain Monitoring
But it’s important to know that imaging of the glymphatic system in humans is not yet possible. Therefore, additional research is needed to establish a causal relationship between neurodegenerative disease and supine sleep.
Source: Alzheimers Weekly