Symptoms of increasing anxiety may be an early warning sign of Alzheimer's disease years before cognitive impairment is evident, a new study suggests.
Researchers have long studied the risk factors that increase the chances of developing Alzheimer's – including neuropsychiatric conditions such as depression. Now, scientists say anxiety symptoms could be a dynamic marker of the disease's early stages.
"Rather than just looking at depression as a total score, we looked at specific symptoms such as anxiety," explains geriatric psychiatrist Nancy Donovan from Brigham and Women's Hospital in Boston, Massachusetts.
"When compared to other symptoms of depression such as sadness or loss of interest, anxiety symptoms increased over time in those with higher amyloid beta levels in the brain."
Amyloid beta is a protein that's comprehensively been linked to Alzheimer's disease, building up in the brain in clumps that form plaques and disrupting communication between neurons.
That disruption is thought to be a chief culprit behind the cognitive impairment of Alzheimer's disease, but it could also be implicated in the condition's pre-clinical phase, potentially as far back as 10 years before memory decline is diagnosed.
Donovan and fellow researchers examined data from the Harvard Ageing Brain Study, an observational, five-year study of 270 healthy men and women aged between 62 and 90 with no active psychiatric disorders.
Amongst other tests, participants underwent brain scans and were analysed for depression on a yearly basis. Over the course of the study, the team found higher levels of amyloid beta in the brain were associated with increasing anxiety symptoms in the cohort.
"This suggests that anxiety symptoms could be a manifestation of Alzheimer's disease prior to the onset of cognitive impairment," Donovan says.
"If further research substantiates anxiety as an early indicator, it would be important for not only identifying people early on with the disease, but also, treating it and potentially slowing or preventing the disease process early on."
At this point, the researchers acknowledge there's still a lot we don't know about how this association between anxiety and amyloid beta comes about – and it's worth emphasising that further longitudinal follow-ups will be required to verify whether participants exhibiting escalating anxiety go on to develop Alzheimer's as well.
Right now, that hasn't been demonstrated, but in the absence of a single, widely used biomarker for early Alzheimer's detection, the team thinks anxiety testing could be a useful tool – even if only to help narrow the field of which patients may be at most risk.
"This is not a definitive result, but it does strengthen the argument that neuropsychiatric changes might be associated with this amyloid," Donovan explained to the Boston Herald.
"As a screening mechanism, it's probably not sensitive enough, but if you can measure multiple risk factors in the same individuals, then it becomes more useful."
The findings are reported in The American Journal of Psychiatry.