Anxiety has biological basis in the brain

New research provides the best evidence to date that anxiety and agitation displayed late in the day, and sometimes seen in older adults, especially those with dementia, has a biological basis in the brain.

The findings could help explain “sundowning”, a syndrome where older adults show high levels of anxiety, agitation, general activity and delirium in late afternoon and evening, before they would normally go to bed.

Lead author of the study and doctoral student in neuroscience at Ohio State University, Tracy Bedrosian, said “sundowning” was a big problem for caregivers.

“Patients can get aggressive and very disruptive,” Ms Bedrosian said.

“There have been a few clinical studies documenting sundowning, but until now there hasn’t been research in animals to see what’s going on in the brain to explain this,” she said.

The new study found that aged mice showed significantly more activity and more anxiety-like behaviours in the hours before they would normally sleep when compared to middle-aged mice.

In these aged mice, the researchers found changes in parts of their brain associated with attention, emotions, and arousal, all of which could be associated with the sundowning behaviour seen in humans.

In addition, mice that were genetically engineered to have an Alzheimer’s-like disease also showed more anxiety before sleep than did other mice.

Co-author of the study, Randy Nelson, said some people have argued sundowning could be explained just by a build-up of frustration of older people who cannot communicate their needs over the course of the day, or by other factors.

“But our findings suggest there is a real phenomenon going on here that has a biological basis,” he continued.

In the first experiment, researchers compared middle-aged adult mice (seven months old) with aged mice (29 months old) that would resemble humans in their 80s.

Results showed the aged mice were significantly more active than middle-aged mice in the two to three 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. But the aged mice had a flattened rhythm in which they showed the same level of activity throughout their active period.

These findings indicate that in the evening, when the middle aged mice would slow down compared to their peak activity levels, the aged mice kept going.

The middle-aged mice showed consistent levels of anxiety during most of the day. However, the aged mice showed more anxiety when tested soon before they would have gone to sleep.

There were also differences in the brains of the aged mice when compared to the middle aged mice. The researchers looked specifically at the cholinergic system, because loss of function in that system is associated with dementia and many of the circadian changes associated with ageing.

Findings in aged mice showed a higher level of acetylcholinesterase – an enzyme associated with anxiety and agitation – before sleep than earlier in the day.

Drugs used to control levels of acetylcholinesterase are sometimes used on dementia patients, although there has been no research to suggest it has an effect on sundowning.

Do you know of any dementia sufferers who display behaviours similar to “sundowning”? How do they manage their anxiety? Share your suggestions below.