People with a common type of irregular heart rhythm called atrial fibrillation (AF) are also more likely to decline mentally or develop dementia, according to a study in Annals of Internal Medicine.
The link between AF and strokes is well established. Irregular beating of the heart's upper chambers (atria) may form blood clots. A clot could then travel to the brain, interrupt blood flow, and cause a stroke. Researchers assumed this would explain the link between AF and cognitive decline, but it hasn't been proved.
Researchers pooled findings from previous studies on the connection of AF to cognitive decline in people both with and without a history of strokes. The link held for both cognitive decline and dementia. (Alzheimer's disease is the most common form of dementia in older adults.) One possible explanation is that people with AF have small "silent" strokes that damage the brain without triggering obvious symptoms. Researchers will also want to figure out if treating AF helps to reduce mental decline later in life. In the meantime, the study is one more reason for people with AF to seek the best treatment available.