MURRAY, UTAH. The majority of patients with atrial fibrillation (AF) have underlying heart disease. Only about 20% have what is known as lone atrial fibrillation (LAF), that is, afib without underlying heart disease. The risk of afib increases with age, diabetes, hypertension, and systemic inflammation. These risk factors are identical to those observed for dementia. Alzheimer's disease (AD) is the most common form of dementia in the elderly (60-80% of cases), followed by vascular dementia (10-20% of cases). Recent research has observed that AD tends to progress faster in patients with AF than in those free of afib. This observation is not really surprising since AD and AF share the same risk factors.
Researchers at the Intermountain Medical Center now report that AF is independently associated with AD. Their study involved 37,025 consecutive patients with heart disease who were examined by cardiologists and then enrolled in the Intermountain Heart Collaborative Study. Patients with existing AD or AF were excluded. During 5 years of follow-up, 10,161 (27%) developed AF and 1,535 (4.1%) were diagnosed with some form of dementia (23% Alzheimer's, 21% senile dementia, 12% vascular dementia, and 44% non-specified dementia). Patients with dementia were older and had higher rates of hypertension, coronary artery disease, renal failure, heart failure, and prior stroke – in other words, a very sick group of people, and in no way comparable to a group of otherwise healthy lone afibbers.
About 50% of the patients who developed dementia also developed AF and in all cases the diagnosis of AF came before the diagnosis of dementia. Somewhat surprisingly, the association between AF and dementia was strongest in the age group 70 years or younger. The presence of AF also identified dementia patients who were at an increased risk of dying prematurely.
Bunch, TJ, et al. Atrial fibrillation is independently associated with senile, vascular, and Alzheimer's dementia. Heart Rhythm, Vol. 7, April 2010, pp. 433-37
Editor's comment: The conclusion that AF and dementia are associated is not really surprising since both share the same underlying causes – none of which apply to LONE atrial fibrillation.