Methods of treating cognitive impairment, and/or reducing or preventing one or more neuropsychiatric morbidities in a subject with a neurodegenerative disease or disorder are disclosed. The methods can include administering the subject an effective amount of a (1-piperidinylalkyl)pyrimidinone derivative, preferably ritanserin, or a pharmaceutically acceptable salt thereof, to increase slow wave sleep； to increase dopamine signaling, preferably in the brain, more preferably in the prefrontal cortex； to increase the expression of BDNF preferably in the brain, more preferably in the hippocampus； or a combination thereof. Typically, the compound is administered in a pharmaceutical composition including a pharmaceutically acceptable carrier or excipient. In some embodiments, the subject has not been clinically diagnosed with neurodegenerative disease based on physical symptoms.
