Feelings of apprehension and fear are often observed in those suffering mild cognitive impairment (MCI), and previous research has suggested that anxiety could be an early indicator for Alzheimer's disease, which often follows MCI. Now a new study has found an association between anxiety and an increased rate of progression from MCI to Alzheimer's disease.]
For the study, conducted at the Medical University of South Carolina (MUSC), researchers assembled a group of 339 patients with an average age of 72 years from the Alzheimer's Neuroimaging Initiative 2 cohort. All members of the study group had a baseline diagnosis of MCI, with 72 progressing to Alzheimer's while the remaining 267 stayed stable. MRI's were also conducted so as to determine the baseline volumes of the hippocampus and the entorhinal cortex, two brain regions important for memory formation.
"We know that volume loss in certain areas of the brain is a factor that predicts progression to Alzheimer’s disease," says study senior author Maria Vittoria Spampinato, M.D., professor of radiology at MUSC. "In this study, we wanted to see if anxiety had an effect on brain structure, or if the effect of anxiety was independent from brain structure in favoring the progression of disease."
The study participants were also tested for the presence of the APOE ε4 allele, which is recognized as the most prevalent risk factor for Alzheimer's and is associated with an earlier age of onset of the disease. Finally, established clinical surveys were used to measure anxiety.
The researchers found that hippocampus and entorhinal cortex of those study participants that progressed to Alzheimer's were significantly lower in volume to those that didn't and that this group also had a greater frequency of the APOE ε4 allele. Both these findings were as the researchers expected, but they also found that anxiety was associated with cognitive decline independently of these other factors.
"Mild cognitive impairment patients with anxiety symptoms developed Alzheimer’s disease faster than individuals without anxiety, independently of whether they had a genetic risk factor for Alzheimer’s disease or brain volume loss," says study first author Jenny L. Ulber, a medical student at MUSC.
The researchers say the link between symptoms of anxiety and an increased rate of progression from MCI to Alzheimer's could help improve screening and management of patients with early MCI. However, they point out that is still unclear whether anxiety is a cause or effect of the faster progression.
"We need to better understand the association between anxiety disorders and cognitive decline," argues Dr. Spampinato. "We don’t know yet if the anxiety is a symptom – in other words, their memory is getting worse and they become anxious – or if anxiety contributes to cognitive decline. If we were able in the future to find that anxiety is actually causing progression, then we should more aggressively screen for anxiety disorders in the elderly.”
Ulber adds that many hospitals screen the elderly for depression and suggests that maybe this population should also be screened for anxiety disorders.
"Middle-aged and elderly individuals with high levels of anxiety may benefit from intervention, whether it be pharmacological or cognitive behavioral therapy, with the goal of slowing cognitive decline," she says.
As this study was based on single MRI scans, in future the researchers would like follow-up scans to be obtained in an effort to look at changes over time and see if anxiety plays a role on the speed of brain damage progression. They would also more closely examine whether gender differences have an impact on the link between anxiety and cognitive decline.