Common irregular heartbeat raises risk of
dementia
August 8, 2011—The most
common kind of chronically irregular
heartbeat, known as atrial fibrillation, is
associated with a greater risk of dementia,
including Alzheimer's disease.
This discovery by
scientists at Group Health Research
Institute and their collaborators was
published online in advance of print on
August 1 in the Journal of the American
Geriatrics Society.
"Both atrial
fibrillation and dementia increase with
age," said Sascha Dublin, MD, PhD, a Group
Health Research Institute assistant
investigator who led the research.
"Before
our prospective cohort study, we knew that atrial fibrillation can cause stroke, which
can lead to dementia. Now we've learned that
atrial fibrillation may increase dementia
risk in other, more subtle ways as well."
The results of Dr.
Dublin's study suggest a relationship
between atrial fibrillation and dementia
beyond the connection through stroke. The
people in the study had a mean age of 74
years when the study began. None had
dementia or a history of stroke.
At the beginning of the
study, 4.3 percent had atrial fibrillation,
and an additional 12.2 percent developed it
during the study. In the course of the
study, 18.8 percent developed some type of
dementia. People with atrial fibrillation
were more likely to have other
cardiovascular risk factors and disease than
were those without the condition.
So the researchers
looked to see if atrial fibrillation
increased dementia risk more than just
through its association with other kinds of
heart disease.
Participants were
followed for an average of seven years. Over
this time, those with atrial fibrillation
had a 40 percent to 50 percent higher risk
of developing dementia of any type,
including probable Alzheimer's disease,
compared to those without atrial
fibrillation. This was true even for people
who did not also have a stroke during the
follow-up period.
The research was part of
Adult Changes in Thought (ACT), an ongoing
joint project of the Group Health and
University of Washington studying risk
factors for dementia in older adults.
Started in 1994 ACT is led by Dr. Dublin's
co-author Group Health Vice President for
Research and Group Health Research Institute
Executive Director Eric B. Larson, MD, MPH.
ACT focuses on finding
ways to delay or prevent dementia, including
Alzheimer's disease, and declines in memory
and thinking.
It aims to deepen
understanding of how the body—especially the
brain—ages. ACT participants are members of
Group Health Cooperative, a nonprofit health
care system in the U.S. Pacific Northwest.
Dr. Dublin's study,
which ran from 1994 to 2008, followed 3,045
people. The researchers relied on Group
Health's advanced electronic data systems to
determine whether participants had atrial
fibrillation. The cognitive function of all
study participants was evaluated every two
years with tests and interviews as part of
ACT.
Patients whose ACT tests
indicated possible dementia had additional
tests including physical, neurological, and
psychological exams, and many also had brain
scans. A panel of experts determined the
correct diagnosis for patients with
cognitive problems.
Atrial fibrillation
affects 3 million Americans. Dr. Dublin says
that some ways it might increase dementia
risk are:
-
weakening the heart's pumping ability,
leading to less oxygen going to the
brain;
-
increasing the chance of tiny blood
clots going to the brain, causing small,
clinically undetected strokes;
-
a combination of these plus other
factors that contribute to dementia such
as inflammation.
Dr. Dublin said an
important next step is studying whether any
treatments for atrial fibrillation reduce
the risk of developing dementia. The
researchers also hope their results reach
primary care providers, who are often the
main doctors caring for people with atrial
fibrillation, dementia, or both.
"Right now, we think we
are protecting our patients' brains as long
as they don't have a stroke, but tiny
insults over time can add up," said Dr.
Dublin, who is a primary care physician at
Group Health. "This paper is a wakeup call,
telling us that we need to learn more about
how to protect brain function, while
continuing to give patients with atrial
fibrillation the best possible care."
###
The National Institute
on Aging, part of the National Institutes of
Health, funded this study.
