The American Heart Association (AHA) has issued a new scientific statement on the link between heart failure (HF), atrial fibrillation (AF), and coronary heart disease (CHD) and the increased risk for cognitive impairment and dementia.
The statement includes an extensive research review and offers compelling evidence of the inextricable link between heart health and brain health, which investigators said underscores the benefit of early intervention.
The cumulative evidence “confirms that the trajectories of cardiac health and brain health are inextricably intertwined through modifiable and nonmodifiable factors,” the authors wrote.
Investigators say the findings reinforce the message that addressing cardiovascular health early in life may deter the onset or progression of cognitive impairment later on.
And the earlier this is done, the better, lead author Fernando D. Testai, MD, PhD, a professor of neurology and the vascular neurology section head, Department of Neurology and Rehabilitation, University of Illinois, Chicago, told Medscape Medical News.
The statement was published online on October 10 in Stroke.
Bridging the Research Gap
It’s well known that there’s a bidirectional relationship between heart and brain function. For example, HF can lead to decreased blood flow that can damage the brain, and stroke in some areas of the brain can affect the heart.
However, that’s only part of the puzzle and doesn’t address all the gaps in the understanding of how cardiovascular disease contributes to cognition, said Testai.
“What we’re trying to do here is to go one step further and describe other connections between the heart and the brain,” he said.
Investigators carried out an extensive PubMed search for HF, AF, and CHD. Researchers detailed the frequency of each condition, mechanisms by which they might cause cognitive impairment, and prospects for prevention and treatment to maintain brain health.
A recurring theme in the paper is the role of inflammation. Evidence shows there are “remarkable similarities in the inflammatory response that takes place,” with both cardiac disease and cognitive decline, said Testai.
Another potential shared mechanism relates to biomarkers, particularly amyloid, which is strongly linked to Alzheimer’s disease.
“But some studies show amyloid can also be present in the heart, especially in patients who have decreased ejection fraction,” said Testai.
Robust Heart/Brain Connection
The statement’s authors collected a substantial amount of evidence showing vascular risk factors such as hypertension and diabetes “can change how the brain processes and clears up amyloid,” Testai added.
The paper also provides a compilation of evidence of shared genetic predispositions when it comes to heart and brain disorders.
“We noticed that some genetic signatures that have historically been associated with heart disease seem to also correlate with structural changes in the brain. That means that at the end of the day, some patients may be born with a genetic predisposition to developing both conditions,” said Testai.
This indicates that the link between the two organs “begins as early as conception” and underscores the importance of adopting healthy lifestyle habits as early as possible, he added.
“That means you can avoid bad habits that eventually lead to hypertension, diabetes, and cholesterol, that eventually will lead to cardiac disease, which eventually will lead to stroke, which eventually will lead to cognitive decline,” Testai noted.
However, cardiovascular health is more complicated than having good genes and adhering to a healthy lifestyle. It’s not clear, for example, why some people who should be predisposed to developing heart disease do not develop it, something Testai refers to as enhanced “resilience.”
For example, Hispanic or Latino patients, who have relatively poor cardiovascular risk factor profiles, seem to be less susceptible to developing cardiac disease.
More Research Needed
While genetics may partly explain the paradox, Testai believes other protective factors are at play, including strong social support networks.
Testai referred to the AHA’s “Life’s Essential 8” — the eight components of cardiovascular health. These include a healthy diet, participation in physical activity, nicotine avoidance, healthy sleep, healthy weight, and healthy levels of blood lipids, blood glucose, and blood pressure.
More evidence is needed to show that effective management of cardiac disease positively affects cognition. Currently, cognitive measures are rarely included in studies examining various heart disease treatments, said Testai.
“There should probably be an effort to include brain health outcomes in some of the cardiac literature to make sure we can also measure whether the intervention in the heart leads to an advantage for the brain,” he said.
More research is also needed to determine whether immunomodulation has a beneficial effect on the cognitive trajectory, the statement’s authors noted.
They point out that the interpretation and generalizability of the studies described in the statement are confounded by disparate methodologies, including small sample sizes, cross-sectional designs, and underrepresentation of Black and Hispanic individuals.
‘An Important Step’
Reached for a comment, Natalia S. Rost, MD, Chief of the Stroke Division at Massachusetts General Hospital and professor of neurology at Harvard Medical School in Boston, said this paper “is an important step” in terms of pulling together pertinent information on the topic of heart-brain health.
She praised the authors for gathering evidence on risk factors related to AF, HF, and CHD, which is “the part of the puzzle that is controllable.”
This helps reinforce the message that controlling vascular risk factors helps with brain health, said Rost.
But brain health is “much more complex than just vascular health,” she said. It includes other elements such as freedom from epilepsy, migraine, traumatic brain injury, and adult learning disabilities.
No relevant conflicts of interest were disclosed.