Understanding that there is a correlation between atrial fibrillation and Alzheimer's in younger people will allow doctors and patients to either work at preventing the disorder, or treating it early when a diagnosis has been made, he said. Picking up "silent" cases would require testing that's not normally done on younger people, Bunch said.

The study also found:

Patients of any age with AF were 44 percent more likely to develop dementia than patients without the heart disorder.

Younger patients with AF were at higher risk of developing all types of dementia, particularly Alzheimer's.

Patients who have both AF and dementia were 61 percent more likely to die during the study period than dementia patients without the rhythm problem.

Younger AF patients with dementia may be at higher risk of death than older AF patients with dementia.

Alzheimer's disease affects approximately 5.3 million Americans and is the most common form of dementia, accounting for 60 percent to 80 percent of all dementia cases. It is the sixth leading cause of death in the United States.

The study was conducted using five years of data from the Intermountain Heart Collaborative Study, a vast database created with information from hundreds of thousands of patients treated at Intermountain Healthcare hospitals. Data from 37,025 patients was included, and of that group, 10,161 developed AF and 1,535 developed dementia during the study period.

"Now that we've established this link, our focus will be to see if early treatment of atrial fibrillation can prevent dementia or the development of Alzheimer's disease," said Dr. John Day, a cardiologist and director of heart rhythm services at IMC. Day is a co-author of the study.

Bunch expects the findings will spur additional studies to confirm their conclusions and to examine whether early intervention with AF patients can actually alter the outcome and prevent the onset of Alzheimer's.

E-mail: carrie@desnews.com