People who experienced high anxiety at any time in their lives had a 48% higher risk of developing dementia compared with those who had not, according to research published in the journal Alzheimer’s & Dementia.
While many other studies have examined the link between dementia and depression or neuroticism, this study found that the link between anxiety and dementia was independent of depression as a risk factor.
“Anxiety, especially in older adults, has been relatively understudied compared to depression,” Andrew Petkus, PhD, postdoctoral research associate of psychology at University of Southern California said in a statement. “Depression seems more evident in adulthood, but it’s usually episodic. Anxiety, though, tends to be a chronic lifelong problem, and that’s why people tend to write off anxiety as part of someone’s personality.”
USC-led researchers studied 28 years of data from the Swedish Adoption Twin Study of Aging, overseen by the Karolinska Institute of Sweden. The study included 1082 participants who were either fraternal or identical twins, and participants answered several questionnaires, completed in-person tests every three years, and were screened for dementia throughout the study.
The researchers noted that while the participants self-reported their levels of anxiety, which may or may not have met the clinical diagnostic threshold of a psychiatric anxiety disorder, the twin who developed dementia had a history of higher levels of anxiety compared with the twin who did not develop dementia.
Participants with anxiety who later developed dementia “are people that experience more than usual symptoms of anxiety,” Margaret Gatz, PhD, a professor of psychology who also holds joint appointments in the USC Davis School of Gerontology and the Keck School of Medicine, said in a statement. “They are people who you would say operate at a ‘high level of anxiety.’ They are frantic, frazzled people.”
The relationship between anxiety and dementia may be because people with high levels of anxiety tend to have higher levels of stress hormones, including cortisol, which at chronically high levels can damage parts of the brain such as the hippocampus, which stores memory, and frontal cortex, which is responsible for high-level thinking.
The researchers also found that among fraternal twins in which only one twin developed dementia, the association between anxiety and dementia was stronger than in identical twins. This may indicate that there may be genetic factors that account for the anxiety-dementia risk.
In future studies, the researchers hope to determine whether people treated for anxiety earlier in life show a lower risk of dementia compared with people who don’t get treatment for anxiety.
Petkus AJ, et al. Anxiety is associated with increased risk of dementia in older Swedish twins. Alzheimers Dement. 2015; doi:10.1016/j.jalz.2015.09.008.