Sundowning: Is there a specific time of day that it happens or is it the darkness that brings it on?

Memecitamd: Sundowning is typically a late afternoon occurrence.

I notice a slight change at about 3:30 p.m., but 4:30 p.m. seems to be the "witching hour". From having a near-normal conversation to just confusion, complete memory lapses, nonsense speaking, etc. And later in the night (most often during the late night/early morning) anxiety/agitation.

Personally for me I see a large difference in my mom's cognition on gloomy and rainy days. Sunny nice days I go to moms she is almost her normal self, everyday that I go and it's gloomy she a lot more confused

Sundowning is most common late in the afternoon hence the name, however it can occur any time of day.

In my experience, it generally happens in the late afternoon/early evening. When it first started, it would occur at about 3-3:30pm. As the disease progressed, it moved to more in the 5-530pm range. Later, we went through a period where it would occur at 830-900pm after he went to bed. I have also found it to occur occasionally very early in the morning when he wakes up. With all that said, I think that sundowners is much most everything with dementia, it varies from person to person and it can change in the same person over time. What has helped me the best in dealing with sundowners is learning to recognize the signs that it was about to occur. The signs are fairly subtle and you don’t get much time between when the signs start and the sundowners hits full force, but my father is initially compliant and so I can get his Xanax in him before it gets bad. Then, I just have to wait for the 15-20 minutes for the medication to kick in. I imagine the signs can vary from person to person, but my father will start aggressively scratching his head, kicking his feet, or wringing his hands.

We found magnesium glycinate given at around 4 pm helped reduce symptoms.

It got the name "sundowning" because it tends to happen in the latter part of the day.

https://www.agingcare.com/topics/19/sundowners-syndrome

The medical community really doesn't know why it happens. It could be how the demented mind interprets light, it could be they are more tired and anxious as the day progresses... there is not real way to study it since people with dementia cannot accurately answer questions and oftentimes don't interpret their body signals accurately anymore.