In a cross-sectional population-based study in dementia-free people (age ≥ 60 years, n = 841), long sleep duration (> 8 h versus normal sleep: 6–8 h) measured objectively was associated with lower Aβ42/Aβ40 and higher plasma Aβ40 and total-tau [39]. The gene discussed is MAPT; the disease is dementia.