A study of 227 individuals with Long COVID-related neurocognitive symptoms found a 59% increase in plasma pTau-181, a protein biomarker linked to Alzheimer's disease and neurodegeneration, compared to pre-COVID levels and unaffected controls. Elevated tau levels were most pronounced in patients with symptoms lasting over 1.5 years, suggesting prolonged neurological injury, though researchers caution that further studies are needed to determine if this reflects progressive brain pathology or increased dementia risk.