Atrial fibrillation not a risk factor for dementia
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While atrial fibrillation is a significant risk factor for stroke in the very elderly, it does not predict dementia, according to findings published in the medical journal Stroke.
Atrial fibrillation is a heart rhythm disorder (arrhythmia) of the upper chambers of the heart (atria), resulting in disorganized and abnormal contractions, Dr. Tuula Pirttila, of Kuopio University Hospital, Finland, and colleagues report. “Several studies have shown that atrial fibrillation predicts the development of poststroke dementia, whereas others have found no such association.”
In a 9-year population study in Vantaa, a town in Southern Finland, the researchers examined the association between atrial fibrillation, stroke, dementia, and their correlation with brain disorders in subjects who were 85 years of age or older.
A total of 553 patients were examined by a neurologist. The diagnosis of atrial fibrillation was made by ECG or medical record review. During an average follow-up of 3.5 years, 479 subjects died, and postmortem examinations were performed in 306.
Overall, 22.1 percent were diagnosed with atrial fibrillation. A significant association was observed between atrial fibrillation and stroke. Stroke was present in 32 percent of 122 subjects with atrial fibrillation and in 16.7 percent of 431 subjects without atrial fibrillation.
Dementia that was present at the beginning of the study was much more common among subjects who had a stroke than among those who did not (71.2 percent versus 30.5 percent), the investigators report, but the frequency of dementia did not differ between those with or without atrial fibrillation.
During follow-up, 100 new dementia cases occurred. Again, the incidence of dementia was not significantly different in those with or without atrial fibrillation, at 16.4 percent and 18.6 percent, respectively.
Factors associated with dementia included education, beta-amyloid load in the brain, and blood vessel disease, but sex, age at death, or APOE e4 allele, the gene mutation for Alzheimer’s disease, were not, Pirttila’s team reports.
They conclude that atrial fibrillation can be considered a contributor to dementia in the very old, through its relation to stroke, but “it is not an independent predictor of dementia.”
SOURCE: Stroke, May, 2007.
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