Biological basis for "sundowning".

• Position: The Elderly - Dementia - Brief article

Late-day anxiety and agitation sometimes seen in older institutionalized adults, especially those with dementia, have a biological basis in the brain, according to a study published in the Proceedings of the National Academy of Sciences. The findings could help explain "sundowning," a syndrome in which older adults show high levels of anxiety, agitation, and delirium in late afternoon and evening before they normally would go to bed.

"It's a big problem for caregivers. Patients can get aggressive and very disruptive," points out Tracy Bedresian, lead author of the study. "There have been a few clinical studies documenting sundowning but, until now, there hasn't been research to see what's going on in the brain to explain this."

Researchers found changes in parts of the brain associated with attention, emotions, and arousal, all of which could be associated with the behavior seen in sundowning. "Some people have argued that sundowning could be explained just by a buildup of...