Could Anxiety be an Early Indicator of Alzheimer's Disease?

New US research suggests that there may be a link between an increase in symptoms of anxiety and a risk of developing Alzheimer's disease.

The most common form of dementia, Alzheimer's disease causes the decline of cognitive function, which eventually becomes severe enough to leave sufferers unable to carry out daily tasks and activities.

A main cause of the disease is thought to be the buildup of proteins amyloid beta and tau in the brain. Amyloid beta can fold and form into plaques which build up in the spaces between nerve cells, while tau forms into tangles which build up inside cells.

Previous research has suggested that depression and other neuropsychiatric symptoms may be predictors of the progression of Alzheimer's disease during its "preclinical" phase -- the stage of the disease where amyloid beta and tau can accumulate in the brain, and which can occur more than a decade before the onset of symptoms can be seen by individuals or physicians.

To look at a possible link between levels of amyloid beta and measures of depression and depressive symptoms in cognitively normal, older adults, researchers from Brigham and Women's Hospital gathered data from 270 male and female participants aged between 62 and 90 years old.

Participants underwent baseline imaging scans, commonly used in studies of Alzheimer's disease, and completed annual assessments to detect depression in older adults.

The team calculated total scores over five years for depression, as well as scores for three symptoms of depression: apathy-anhedonia -- a lack of emotion and loss of interest in activities, dysphoria -- a state of unease and dissatisfaction, and anxiety.

The results showed that a higher level of amyloid beta was associated with increasing anxiety symptoms over time, suggesting that worsening anxiety may be an early indicator of Alzheimer's disease.

"Rather than just looking at depression as a total score, we looked at specific symptoms such as anxiety. 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," said first author Nancy Donovan.

"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," she added.

The findings can be found published online in The American Journal of Psychiatry.