Always tired

My DH does, as well. I know that this is part of the illness but wanting to know more I turned to google. Here is the answer:

People with Alzheimer's disease often experience excessive daytime sleepiness due to the degeneration of neurons that promote wakefulness in the brain. This can lead to frequent napping and difficulty staying awake, especially in the later stages of the disease.

My DH began this in stage 3. As you probably know, behaviors are not always consistant with the supposed stage is which they are most common. If DH does this in the evening, I will wake him after about 15 minutes so that he will be able to sleep during the night.