Question:
Recently a friend of mine starting working in a dementia ward for severelydemented individuals. She was advised by other staff that to be carefulafter sundown because many of the patients become violent and extremelydifficult to control. I'm mystified by this, just wondering if anyone elsehas noticed this in severe dementia and\or if they have any ideas re thesame. I did note a few months ago a report stating that bright light therapyproved beneficial for some dementia patients but this doesn't account forthe above observations.

Answer: This phenomenon occurs in delirium, e.g. post-op delirium, DTs etc.There is always a clear worsening in the evening. Delirious people seemalmost lucid in the daytime and off the planet at night. 15-20% ofgeneral hospital patients are delirious at any point in time.

It seem to be due to the reduced sensory (mainly visual) input thatoccurs at sunset. The degree of reduction in light between full daylight and a well light room at night is actually massive (at leasthundred fold difference). A dimly light room is the worse. A totallydark room is actually better.

Of course, the intact brain copes with this easily, but the impairedbrain (i.e. delirium) does not cope and starts to experience sensorydistortions (illusions) and hallucinations (mainly visual). Disturbedbehaviour may then result in response to this.

Dementia patients, who are in care, are usually well advanced andexperience delirium very easily. Urinary tract infection, constipationbeing some of the more common mundane triggers for this.

Delirium literally means "out of (de) the furrow (lirium)" [Latin].Dementia means "out of one's mind" and originally referred more topsychosis than organic impairment.