After observing sundowning in my husband for the past several years, it occurs to me that it has nothing to do with the position of the sun, as days [especially here in the northern part of the US] can be really long with the sun not setting until 9pm in the spring while it gets dark by 4PM in late fall and winter. It makes no difference, as he gets his restlessness, increased delusions, anxiety and agitation after dinner and usually calms down by bedtime. As he doesn't get his PM meds until bedtime, his calming down is not med-related. There is no change between seasons.

Here is something I found from the AD and from what I have heard sundowning is not that common in LBD but we certainly had it in our home! I actually think it had to do with the fatigue of the day not actually the time or the daylight!

http://www.mayoclinic.com/health/sundowning/HQ01463

Thanks, Irene. The article says 'the cause isn't known', so I guess that answers my question. Nothing seems to help. I just mentally and emotionally prepare for the three or four hours of agitation & anxiety he has every evening. I think reassurance helps as much as anything. Usually I'm very tired by then, myself, so it sometimes takes all I can muster to engage him rather than hide in another room.

Pat,
I hear you! Not a very rewarding job is it ?

Wow, the idea that Dad's evening problems may be related to fatigue makes sense. I will reflect a bit and try to decide whether they are related to being overactive during the day or whether they are related to being trapped in a small, locked unit (which has been my assumption until now). Ironically, assuming that he's struggling against being trapped has led me to provide him with a more active, off-ward schedule during the day. Perhaps it is less running around that he needs. This puts me in mind of some sage advice I got about periodically reviewing Dad's lifestyle to see if he's able to keep up with it. Thank you so much, friends!

Sue,
I think this fatigue is just part of them no matter what they do honestly, I say as long as you can get him to do some things, go for it !

There are several good past discussions here of sundowning. One, in particular, that I like is:
viewtopic.php?f=2&t=330