Afib Linked to Dementia Incidence and Mortality
By Crystal Phend, Senior Staff Writer, MedPage Today
Published: April 02, 2010
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and
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■Caution interested patients that the observational study could not determine whether atrial fibrillation caused dementia or vice versa and could not establish mechanisms for the associations seen.

Atrial fibrillation appears independently linked to all forms of dementia, particularly in later middle age, researchers found.

Atrial fibrillation patients 70 or younger were 2.3 times more likely to develop Alzheimer's disease than those without the heart rhythm disorder, after multivariate adjustment (P=0.001), in a large prospective cohort study by T. Jared Bunch, MD, of Intermountain Medical Center in Murray, Utah, and colleagues.

This younger group with atrial fibrillation was also at elevated risk of senile dementia (adjusted OR 3.34, P<0.0001), vascular dementia (adjusted OR 2.22, P=0.004), and nonspecific dementia (adjusted OR 2.87, P<0.0001), the group reported in the April Heart Rhythm Journal.

Atrial fibrillation also predicted 38% to 45% elevated mortality risk in patients with the different forms of dementia, compared to those without dementia, they found.

Both conditions are increasingly common with age and share other risk factors as well, such as diabetes, hypertension, and systemic inflammation.

However, the finding that the greatest effect was in the youngest group in the study suggested that age alone didn't account for the link, the researchers said.

Furthermore, hypertension was similar between atrial fibrillation and non-atrial fibrillation groups, they noted.

But early inflammation and early vascular disease may be mechanisms, Bunch and colleagues speculated.

"This possibility brings up the question of whether aggressive rhythm management or anticoagulation may improve outcomes," they speculated.

To confirm the independent link between these conditions seen in prior studies, the researchers analyzed results for 37,025 consecutive patients in the ongoing prospective Intermountain Heart Collaborative Study.

Among the participants (mean age 60.1 at baseline), 27% developed atrial fibrillation and 4.1% developed dementia during five-year follow-up.

Dementia incidence was higher among patients with atrial fibrillation overall and for each dementia subtype (all P<0.0001):

•Nonspecified dementia (3.3% versus 1.3%)
•Alzheimer's disease (1.5% versus 0.7%)
•Senile dementia (1.6% versus 0.6%)
•Vascular dementia (0.9% versus 0.3%)

After adjustment for significant baseline and clinical factors, the association with Alzheimer's disease lost statistical significance (OR 1.06, P=0.59).

All other types maintained significance in the multivariate analysis with odds ratios of 1.73 for vascular dementia (P=0.001), 1.39 for senile dementia (P=0.005), and 1.44 for nonspecific dementia (P<0.0001).

All those who developed both conditions developed atrial fibrillation before diagnosis with dementia, but cognitive decline occurred earlier in patients with atrial fibrillation than in those without it.

These associations appeared strongest among those under age 70 in the multivariate analysis, falling into nonsignificance by age 80 to 89 for all categories except senile dementia.

Atrial fibrillation further boosted the mortality risk associated with dementia, with the greatest impact again in the younger groups (70 and younger, HR 1.71 to 2.07, P=0.10 to P=0.002) -- but nonsignificant in the older groups.

The researchers cautioned that their observational study of a large healthcare database could not establish causality or mechanisms for the associations.

Bunch and several co-authors reported relationships with Boston Scientific.

One co-author also reported conflicts of interest with St. Jude Medical.