Anxiety may accelerate the decline into Alzheimer's disease in older patients with mild memory problems, a finding researchers say should serve as a wake-up call for younger Canadians, too.
While the link between depression and Alzheimer's is already well established, little research has been done on how anxiety may contribute to dementia. A new study by Baycrest's Rotman Research Institute in Toronto, supported by the United States National Institutes of Health, used data from the Alzheimer's Disease Neuroimaging Initiative, which documented changes in cognition, brain structure and mental health in 376 adults, ages 55 to 91, with mild cognitive impairment – the kind of memory problems that make people forget what they are about to say or why they went into a particular room.
At points over a three-year period, patients reported whether they felt anxious when separated from a spouse or caregiver, or experienced anxiety symptoms such as shortness of breath, nervousness, shakiness and trembling.
In patients with mild, moderate or severe anxiety, Alzheimer's risk increased by 33 per cent, 78 per cent and 135 per cent, respectively, the researchers found.
The Baycrest study, published online in the American Journal of Geriatric Psychiatry, is the first to identify anxiety as a potential risk marker for Alzheimer's disease in adults diagnosed with mild cognitive impairment.
Dr. Linda Mah, a psychiatrist at the University of Toronto and principal investigator on the study, explained that people with anxiety disorders have higher levels of the stress hormone cortisol, which has been shown to damage the hippocampus, a brain structure important for memory processing and emotion.
"I think we need to take anxiety more seriously," she said.
For people in their 30s and 40s, the study should serve as a "wake-up call," she added. And for older patients, mindfulness-based stress reduction is being studied as a potential intervention. (It will be the focus of a researchers' conference in Toronto in December.) Mah and colleagues were able to separate the effects of anxiety from those of clinical depression, since only patients with low depression scores were included in the study. At the onset, patients were able to function in everyday life, but suffered from memory problems that were mild but considered red flags: "This is not normal aging, but a prodrome [symptom] of Alzheimer's," Mah said.
In patients whose condition deteriorated into Alzheimer's disease, magnetic resonance imaging (MRI) detected structural changes, including atrophy, in brain regions involved in creating memories as well as processing emotions.
Mah said it was unlikely patients' anxiety was simply an emotional response to their cognitive decline. Rather, she theorized that anxiety could be a clinical biomarker of Alzheimer's – "a reflection of worsening disease," she said.
She noted that the study data did not provide a clear picture of whether patients suffered from specific anxiety disorders, or information about any history of clinical anxiety.
In follow-up studies, "I'd like to start looking at anxiety using questionnaires instead of a screening [question]," she said, "and a clinical assessment [of anxiety] would be informative."
Dr. Haakon Nygaard, an Alzheimer's specialist at the University of British Columbia, noted that anxiety levels tend to fluctuate and that patients' responses to a question about anxiety symptoms may have varied at different times. Nevertheless, he described the study as an "important addition" to research on the role of mood disorders in Alzheimer's disease. Previous research looking at depression and emotional stress suggests "there may be shared mechanisms that lead to, or exacerbate, Alzheimer's disease," he said.
Anxiety may not be easy to treat in patients with mild cognitive impairment, since anti-anxiety medications such as benzodiazepines may interfere with sleep and "blunt your cognitive function," Nygaard said.
A better bet is to focus on making lifestyle changes to reduce Alzheimer's risk, he said. People with high anxiety tend to have difficulty sleeping well. According to recent studies, "sleep is very important for clearing these pathologic proteins that build up in Alzheimer's disease," he explained.
Mah suggested that older patients with mild memory problems may benefit from activities such as learning a new dance. "It stimulates your brain, it's social, and it probably would improve mood and reduce stress," she said.
"People really need to take care of the stress they experience in their lives," she added, "and try to live in the present and enjoy things."