Mechanisms behind sleep quality influencing disease severity in neurodegenerative diseases remain speculative: Accumulation of neurotoxic proteins, including α-synuclein (α-syn) in PD and amyloid β-protein (Aβ) and tau in Alzheimer’s disease (AD), is a common pathological mechanism. The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.