Hi Sonia. I'm sorry that your stepfather is experiencing Sundowners now. I have befriended a lady in a local nursing home, and about one month ago, she also began experiencing symptoms of Sundowners Syndrome. Much like your stepfather, she started becoming extremely agitated when it became dark, and during the middle of the night, she also believed that people were entering her room and stealing her things.
I did some research after my friend developed Sundowners because I also wanted to know why she was having so many problems at night. For the most part, it is not yet clearly known why Alzheimer's patients have increased problems at night. Recent research has speculated that the damaged nerve pathways in Alzheimer's patients disrupts the part of the brain which control circadian rhythms. Circadian rhythms control the sleep - wake cycles in our brains. So, as a result, the internal clocks in the Alzheimer's patients are very messed up. People without Alzheimer's are tired and sleepy at night, but the reverse seems to happen to the Alzheimer's patient. That feeling of sleepiness is replaced with feelings of extreme agitation.
Also, because Alzheimer's patients tire easily, they often become more agitated at night, when they are most tired. After my friend in the nursing home developed Sundowners, the doctor suggested that she take more naps during the day, in an effort to curb her increased agitation at night.
In addition, it is believed that Sundowners is exaggerated by a lack of sensory stimulation at night. During the day, the activity and noises can sometimes provide a secure feeling to the Alzheimer's patient. In the nursing home that I visit, almost all of the Alzheimer's patients sleep well during the day, possibly because they feel more secure when there is activity around them. During the night, however, it is usually very quiet and dark, and that can lead to increased restlessness in some patients.
My friend in the nursing home also is very scared that she will be left alone. This feeling has only been intensified now that she has developed Sundowner's. It seems like she doesn't understand what's happening to her, and that is leading to even more problems of agitation.
I hope that your stepfather is able to find some peace soon. I'll be thinking of both of you, and take care.