AF Linked to Earlier, More Rapid Cognitive Decline

Susan Jeffrey

June 07, 2013

A new study shows patients with atrial fibrillation (AF) reach clinical thresholds for cognitive impairment and dementia at earlier ages than those without, even in the absence of clinical stroke.

Over 7 years of follow-up, mean Modified Mini-Mental State Examination (3MSE) scores declined faster after incident AF than among those with no such history.

Although the mechanism linking AF with a more rapid trajectory of cognitive decline is not clear, the authors speculate it could relate to subclinical embolic infarction or cerebral hypoperfusion.

"Further research is needed to learn how the adverse cognitive consequences of atrial fibrillation may be prevented," the researchers, with first author Evan L. Thacker, PhD, from the University of Alabama at Birmingham, conclude.

Their findings were published online June 5 in Neurology.

Cardiovascular Health Study

The new findings add to growing evidence of a link between AF and cognitive problems. A post hoc analysis of the ONTARGET (Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial) and TRANSCEND (Telmisartan Randomized Assessment Study in ACE-Intolerant Subjects with Cardiovascular Disease) trial reported an association between AF and increased cognitive and functional decline in AF patients with or without a history of previous stroke that had been assumed to mediate the relationship. A more recent meta-analysis showed a significant relationship between AF and cognitive impairment and dementia, again independent of stroke history.

For this study, the researchers used data from the Cardiovascular Health Study, a community-based study of 5888 men and women aged 65 years or older enrolled in 1989-1990 or 1992-1993 who were free of both AF or stroke at baseline. Participants were censored for this analysis if they had an incident stroke. Incident AF was identified through hospital discharge diagnostic codes and annual study electrocardiograms.

The primary outcome was the rate of decline in mean scores on the 100-point 3MSE, which was also administered annually up to 9 times. A second cognitive test, the Digital Symbol Substitution Test (DSST), was administered annually up to 10 times.

This analysis included 5150 participants; of these, 552 (10.7%) developed incident AF over a mean of 7 years' follow-up.

The researchers report that mean 3MSE scores declined faster in participants after incident AF was identified than before. In models of 3MSE trajectories, for ages 75 and above, the average rate of decline was about 3 points faster per 5 years of aging in participants after incident AF than in those without prior AF. Confidence intervals suggested that in the underlying population, the difference in rates of decline may be 1 to 5 points faster per 5 years.

"For example, the predicted 5-year decline in mean 3MSE score from age 80 to age 85 was –6.4 points (95% confidence interval [CI]: –7.0, –5.9) for participants without a history of atrial fibrillation, but was –10.3 points (95% CI: –11.8, –8.9) for participants experiencing incident atrial fibrillation at age 80, a 5-year difference of –3.9 points (95% CI: –5.3, –2.5)," they write.

In the DSST models, for ages 70 and above, the average rate of decline was about 2 points faster per 5 years in participants after incident AF relative to those without prior AF, they note.

"To put these differences in context, we can consider the expected magnitude of decline in cognitive scores among people without atrial fibrillation," the authors conclude. "In this study, for participants without atrial fibrillation, aging 5 years was associated with average predicted declines in 3MSE score of less than a point at age 70, about 3 points at age 75, 6 points at age 80, and 14 points at age 85."

"The more rapid decline we observed after incident atrial fibrillation suggests that people with atrial fibrillation are likely to reach thresholds of cognitive impairment or dementia at earlier ages than people with no history of atrial fibrillation."

The study was supported by the National Heart, Lung, and Blood Institute; the National Institute of Neurological Disorders and Stroke; and the National Institute on Aging.

Neurology. Published online June 5, 2013. Abstract

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