The JAMA Neurology study was observational and therefore could not prove that too little or too much sleep causes cognitive problems.
Notes on verification
Multiple independent sources (PubMed, JAMA Network, Alzheimer Europe, and a peer-reviewed citing paper) confirm the study's cross-sectional/observational design and the standard methodological limitation that such designs cannot establish causation. [tier=gold indep_score=0.983 clusters=3 claim_tier=notable | framework convergence=single on the original JAMA Neurology cross-sectional study of A4 study participants (upstreams: Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) study, JAMA Neurology (Winer et al. 2021)) — publishers independent, evidence may not be | kind=empirical eligibility=high (extractor: attributed/high)]
Sources
- How much sleep keeps cognitive decline at bay? - Harvard Health (seed:psychology_and_neuroscience)
- https://pubmed.ncbi.nlm.nih.gov/34459862/ (corroboration)
- https://www.alzheimer-europe.org/news/new-research-jama-neurology-explores-impact-sleep-duration-amyloid-accumulation-and-cognitive?language_content_entity=en (corroboration)
- https://jamanetwork.com/journals/jamaneurology/fullarticle/2783664 (corroboration)
- https://pmc.ncbi.nlm.nih.gov/articles/PMC13343368/ (corroboration)