Atrial fibrillation (AF) is associated with faster cognitive decline and an increased risk of dementia, especially in women, Neurology reports.

Researchers from Sweden enrolled 2,685 people without dementia with an average age of 73 years. Of these, 9.1 per cent had AF at baseline. During the nine-year follow-up, 11.4 per cent developed AF and 14.9 per cent developed dementia.

The researchers could not distinguish between AF subtypes and might have missed asymptomatic AF. Nevertheless, AF was significantly associated with a faster annual decline in scores on the Mini-Mental State Examination, a 40 per cent increased risk of dementia from any cause and an 88 per cent increased risk of vascular and mixed dementia. The 33 per cent increase in the risk of Alzheimer’s disease was not statistically significant.

Women with AF were 46 per cent more likely to develop dementia than those without the arrhythmia. The 27 per cent increase in men was not statistically significant.

“Compromised blood flow caused by atrial fibrillation may affect the brain in a number of ways,” says study author Chengxuan Qiu of the Karolinska Institute and Stockholm University. “We know as people age, the chance of developing atrial fibrillation increases, as does the chance of developing dementia.

“Our research showed a clear link between the two and found that taking blood thinners may actually decrease the risk of dementia.”

Based on an average followup of six years, AF patients who used anticoagulants were 60 per cent less likely to develop dementia. The 84 per cent increased risk in those who used antiplatelets was not statistically significant. Assuming a cause and effect relationship, using anticoagulant drugs to treat all people with AF would have prevented approximately 54 per cent of the dementia cases.

“Additional efforts should be made to increase the use of blood thinners among older people with atrial fibrillation,” Dr Qiu adds.