A reader asks:

 What is sundowning, and what symptoms occur with this? Is light therapy something that should be considered? The individual is suffering from depression, irritablility and abnormal sleep patterns.

Answer:

Sundowning refers to agitated, often disruptive behavior during a regular period each afternoon or evening, seen in some elderly patients with dementia. Patients with dementia also often show the other symptoms you mention. Although the research literature is divided on whether light therapy would alleviate symptoms, we think a standard schedule of morning light therapy is well worth a try. An issue is compliance — that is, will the patient with dementia sit for a light therapy session? In most cases, sessions will have to be monitored and supervised by an aide or family member. Since it is possible that light therapy will not be tolerated by the patient, the procedure should be undertaken only with a doctor’s guidance.