June 30, 2011
New Research to Explain “˜Sundowning’
By Lydia Jennings, Ivanhoe Health Correspondent
(Ivanhoe Newswire) -- A new experiment could help explain sundown syndrome in older adults, especially those with dementia. The exact cause of sundown syndrome is not known, however new research provides evidence that late-day anxiety and agitation has a biological basis in the brain. Found in 80 to 90 year old people, "sundowning" shows high levels of anxiety, agitation, general activity and delirium in the late afternoon and evening, leading up to bedtime.
"As of now there hasn't been much research, especially with animals, into what's happening in the brain to cause sundowning," Tracy Bedrosian, lead author of the study and a doctoral student in neuroscience at Ohio State University, told Ivanhoe.
"We compared elderly mice with middle-aged mice, and we compared their behaviors to see if we could mimic some of the symptoms of sundowning that you see in people," Bedrosian said.
The experiment found that aged mice, 29 months old that would resemble humans in their 80's, showed significantly more activity and more anxiety-like behaviors in the hours before they would go to sleep when compared to middle-aged mice, 7 months old "“ just like sundowning in humans.
Found in the aged mice were changes in parts of their brain associated with attention, emotions, and arousal, all of which could be associated with the behaviors seen in sundowning.
The researchers also found 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 aging.
"We found changes in the cholinergic system in the elderly mice that may be related to the behavioral changes seen," Bedrosian said.
The aged mice showed greater expression of a certain enzyme "“ acetylcholinesterase "“ before sleep than earlier in the day. High levels of this enzyme are associated with anxiety and agitation.
The drugs that are prescribed for dementia and for sundowning affect the same cholinergic system in the brain.
"This study gives some evidence to support the fact that this cholinergic system really is altered in sundowning, and drugs affecting this system may actually be a good thing to pursue," Bedrosian said.
The results show that researchers can successfully use mice to model sundown syndrome, and the researchers plan to use that as a starting point to pursue new therapeutic ideas. They hope to use drugs prescribed to humans on the mice and see if it will help with the activity and anxiety symptoms.
"We'd also like to target certain brain regions to see if we can pin-point what parts of the brain are involved in these behaviors," Bedrosian said.
SOURCE: Proceedings of the National Academy of Sciences, June 29, 2011.