MAPT and Alzheimer disease: Given the prevalence of sleep disturbances in AD and other NDDs, this section discusses evidence for the effect of Aβ and tau on sleep (though these are expanded upon in subsequent sections in regard to protein clearance, degradation and spread), the relationship of sleep impairment with mixed proteinopathies common in AD patients, and, finally, neurodegeneration of the sleep–wake circuitry in AD.