Research conducted in the United States has provided further indications that people who suffer from anxiety could be at a higher risk of developing Alzheimer's disease in later life.
The project was carried out at Brigham and Women's Hospital in Boston and involved data from the Harvard Aging Brain Study, which focused on cognitively normal people between 62 and 90 years old, with no active psychiatric disorders. The aim of the study was to define neurobiological and clinical changes in early Alzheimer's disease.
Participants underwent baseline imaging scans commonly used in Alzheimer's research, as well as annual assessments using the 30-item Geriatric Depression Scale.
Published in the American Journal of Psychiatry, the latest analysis of the data showed a link between worsening anxiety symptoms over time and elevated levels of amyloid beta, the main component of plaques found in the brains of Alzheimer's patients.
This provides support for the previously posited theory that neuropsychiatric symptoms such as anxiety and depression could be an early indicator of amyloid beta build-up, and consequently a warning sign for Alzheimer's.
These symptoms could occur in the preclinical phase of the disease, during which deposits of fibrillar amyloid and pathological tau accumulate in the patient's brain. This can take place more than a decade before the individual shows any signs of cognitive impairment.
Offering more detailed insights into the methods involved in the latest research, first report author Nancy Donovan, MD, a geriatric psychiatrist at Brigham and Women's Hospital, said the team wanted to focus on specific symptoms such as anxiety, rather than evaluating depression as an overall score.
This led to findings that, when compared with other symptoms of depression, such as sadness or loss of interest, anxiety increased over time in people with elevated levels of amyloid beta in the brain.
"This suggests that anxiety symptoms could be a manifestation of Alzheimer's disease prior to the onset of cognitive impairment," Dr Donovan continued.
"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."
Since anxiety is relatively common in older people, the researchers suggested that it could be most useful as a risk marker in those who have other genetic, biological or clinical indicators showing a high risk of Alzheimer's disease.
Dr Donovan also noted that further research is needed to ascertain whether, over time, escalating depressive symptoms give rise to the clinical depression and dementia stages of Alzheimer's development.
Other recent developments in Alzheimer's research have included a new method being used by scientists in the US that could help improve understanding of the structure of the amyloid protein and how it spreads through the brain.
Responding to the findings, Dr Carol Routledge, director of research at Alzheimer’s Research UK, said being able to track different forms of amyloid will "provide a greater understanding of Alzheimer's and, with more development, could help to predict how a person's Alzheimer's may progress in future".