BOSTON — Atrial fibrillation may be a significant cause of dementia, based on links between the two disorders in a study of 37,000 people.
In an analysis that controlled for other cardiovascular disease risk factors, patients with atrial fibrillation (AF) were significantly more likely to develop several types of dementia, compared with people without AF. The increased risk was highest among people younger than 70 years old, in whom AF boosted the risk for dementia by two- to threefold, Dr. T. Jared Bunch said at the Heart Rhythm Society's annual meeting. Patients with both AF and dementia also had a significantly increased risk of dying, compared with patients who had the same dementias but no AF.
“To our knowledge, this is the first large population study to clearly show that having AF puts patients at greater risk” for dementia, Dr. Bunch said in a written statement issued at the time of his talk.
One possible explanation of the link is that patients with AF produce microemboli that cause subclinical strokes, which accumulate and eventually produce dementia. This raises the possibility that “early treatment of AF may reduce microemboli and reduce dementia,” said Dr. Bunch, a cardiac electrophysiologist at Intermountain Medical Center in Salt Lake City.
“We know that a third of the strokes in the elderly are related to AF. Instituting screening to detect AF early and treat it may be a really important way to prevent dementia,” said Dr. Melvin Scheinman, professor of medicine and a cardiac electrophysiologist at the University of California, San Francisco.
Dr. Bunch and his associates reviewed 37,025 people enrolled in the Intermountain Heart Collaborative Study. The group comprised 26,864 people without AF and 10,161 with AF; they were followed for an average of 5 years. Average age was 58 among those without AF, and 68 among those with AF, and 60% of all participants were men.
The researchers tracked the incidence of four types of dementia during follow-up: nonspecific, vascular, senile, and Alzheimer's disease. The incidence of each of these dementia types was significantly more common in patients with AF than in those without AF. Incidence rates in the AF subgroup ranged from 0.8% for vascular dementia to 3.2% for nonspecific dementia. Rates in those without AF ranged from 0.3% for vascular dementia to 1.3% for nonspecific dementia.
In an analysis of incidence rates that controlled for other cardiovascular risk factors, patients with AF generally had an increased risk for all types of dementias, compared with matched people without AF. (See box.) Relative risk was highest among patients younger than 70. The relative risk for Alzheimer's disease was significantly higher with AF only in people younger than 70. The greatest relative risk linked to AF was senile dementia in patients younger than 70, where AF boosted the risk more than threefold.
Another analysis assessed the risk for death among patients with both AF and dementia, compared with those who had dementia only. Patients with both AF and any of the four dementia types had a 40% increased risk of dying during follow-up, compared with patients with dementia but no comorbid AF.
Patients with coexistent AF and dementia may have a worse prognosis because the condition is less well managed in patients who also have dementia, Dr. Bunch added.
'This is the first large population study to clearly show that having AF puts patients at greater risk' for dementia. DR. BUNCH
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