AF associated with elevated risk for dementia regardless of stroke

Adults with atrial fibrillation had a higher risk for dementia than those without atrial fibrillation, regardless of whether they had experienced a stroke, according to the results of a prospective, population-based study.

AF may be a risk factor for dementia because it is associated with stroke and chronic cerebral hypoperfusion, but the results of previous studies were inconsistent, the researchers wrote.

They assessed the relationship between incident and prevalent AF and incident dementia between 1989 and 2010 in 6,514 participants from the Rotterdam Study aged at least 55 years at baseline. They also analyzed whether duration of AF was a factor in onset of dementia.

The primary outcome was incident dementia, defined according to criteria from Diagnostic and Statistical Manual of Mental Disorders, third edition (DSM-III) and the National Institute of Neurological and Communicative Disorders and Stroke – Alzheimer’s Disease and Related Disorders Association. There were 81,483 person-years of follow-up.

Renée F.A.G. de Bruijn, MD, and colleagues found that 4.9% of participants had prevalent AF at baseline and 15.3% developed incident dementia during the study period. Prevalent AF conferred a higher risk for dementia (adjusted HR = 1.33; 95% CI, 1.02-1.73), the researchers wrote.

Among the 6,196 participants without prevalent AF at baseline, 11.7% developed incident AF and 15% developed incident dementia during 79,003 person-years of follow-up, according to de Bruijn, from the departments of epidemiology and neurology, Erasmus Medical Center, Rotterdam, Netherlands, and colleagues.

In participants younger than 67 years, incident AF was associated with increased risk for dementia (adjusted HR = 1.81; 95% CI, 1.11-2.94), but that was not the case for those aged at least 67 years (adjusted HR = 1.12; 95% CI, 0.85-1.46; P for interaction = .02).

de Bruijn and colleagues stratified patients with AF by duration of exposure to AF, and observed an association between elevated dementia risk and duration of exposure among those younger than 67 years, (HR for stratum with longest exposure = 3.3; 95% CI, 1.16-9.38; P for trend = .003), but not those aged at least 67 years (HR for stratum with longest exposure = 0.25; 95% CI, 0.04-1.86; P for trend = .94).

Censoring the results for stroke did not change the results, de Bruijn and colleagues wrote. However, they noted, asymptomatic strokes may still explain the link between AF and dementia.

“Such asymptomatic strokes are often lacunes, which are related to an increased risk of dementia,” they wrote. “Second, the brain is vulnerable to changes in blood flow. Hence, cerebral hypoperfusion due to lower cardiac output in AF could cause damage to nerve cells. Third, a noncausal explanation is shared etiology because AF and dementia share many risk factors, such as hypertension, diabetes and hypercholesterolemia.” – by Erik Swain

Source: www.healio.com