Elderly late-day agitation biological

COLUMBUS, Ohio, June 29 (UPI) -- Late-day anxiety and agitation in older institutionalized adults, especially those with dementia, has a biological basis in the brain, U.S. researchers say.

Lead author Tracy Bedrosian, a doctoral student in neuroscience at Ohio State University, says "sundowning" is a syndrome in which older adults show high levels of anxiety, agitation, general activity and delirium in late afternoon and evening, before they would normally go to bed.

"It's a big problem for caregivers," Bedrosian says in a statement. "Patients can get aggressive and very disruptive."

The study found aged mice showed significantly more activity and more anxiety-like behaviors than middle-aged mice in the hours before they would normally sleep -- similar to sundowning in humans -- Bedrosian says. The study showed aged mice were significantly more active than middle-aged mice in the 2 to 3 hours before they would normally go to sleep.

"The middle-aged mice had a distinct pattern of activity, with three peaks of activity during their waking hours," Bedrosian says. "But the aged mice had a flattened rhythm in which they showed the same level of activity throughout their active period."

In the evening, when the middle aged mice would slow down compared to their peak activity levels, the aged mice kept going, Bedrosian says.

The findings are published in the online Early Edition of the Proceedings of the National Academy of Sciences.