Alzheimer's disease not only damages neurons responsible for maintaining sleep at night, but also neurons responsible for wakefulness during the day.

https://www.ucsf.edu/news/2019/08/415116/alzheimers-disease-destroys-neurons-keep-us-awake

The following is for obstructive sleep apnea (in a mouse model) but applies to Alzheimer's as well.

Long-term intermittent hypoxia (LTIH) exposure in adult mice, modeling oxygenation patterns of moderate–severe obstructive sleep apnea, results in lasting hypersomnolence and is associated with nitration and oxidation injuries in many brain regions, including wake-active regions.

https://www.atsjournals.org/doi/full/10.1164/rccm.200411-1564OC

Just about every type of damage done to the brain in Alzheimer's disease is the result of oxidation and nitration, both of which can partially be reversed as can be the damage they cause.