Three common cardiovascular diseases in adults – heart failure, atrial fibrillation and coronary artery disease – are associated with cognitive impairment and an increased risk of dementia. This is according to the new scientific statement “Cardiac Contributions to Brain Health” from the American Heart Association, published in the journal Stroke.
The scientific statement reviews the latest research on the relationship between cardiovascular health and brain health, including cognitive impairment or neuropsychological dysfunction. The statement emphasizes the interrelationship between the brain and the heart, and how important this relationship is for overall health.
Cardiovascular Disease and Cognitive Impairment
According to Fernando D. Testai, M.D., Ph.D., FAHA, professor of neurology and rehabilitation and fellowship director of vascular neurology at the University of Illinois College of Medicine and medical director of stroke at the University of Illinois Hospital at Chicago, who authored the statement, promoting heart health from an early age is important to prevent cardiovascular disease and cardiac events, protect brain health and reduce the risk of cognitive decline later in life. Dementia is generally regarded as an incurable and relentless disease that cannot be prevented. However, there is evidence that a healthy lifestyle and early detection and treatment of vascular risk factors can help maintain normal brain function and reduce the burden of Alzheimer’s disease and other related dementias.
Heart Failure
Heart failure is a major public health problem due to high blood pressure, obesity and type 2 diabetes. A meta-analysis of previous studies found that nearly 50% of people with heart failure have some form of cognitive impairment, which can affect language, memory and/or executive function. The rate of cognitive problems tends to be higher in people with more severe forms of heart failure.
Heart failure can lead to brain damage in a number of ways. Reduced blood flow can lead to mini-strokes or silent brain injuries. Chronic inflammation and neurohormonal activation, which help maintain the brain environment, also cause brain damage. Obesity and sleep-disordered breathing are common conditions in people with heart failure and are also associated with cognitive dysfunction. Brain changes, such as gray matter volume reduction and/or white matter damage, are common in heart failure and contribute to decreased brain function. New evidence also suggests that people with heart failure and people with neurodegenerative diseases such as Alzheimer’s may share genetic variations.
In patients with severe heart failure, cognitive screening is recommended before surgical interventions as the risk of stroke is increased. Stroke is known to be one of the most common causes of cognitive decline.
Atrial Fibrillation
Atrial fibrillation is the most common cardiac arrhythmia in adults. The link between atrial fibrillation and stroke is well known, but the link between atrial fibrillation and cognitive decline requires further research. A large meta-analysis found that atrial fibrillation increases the risk of cognitive impairment by 39%. Risk factors associated with both atrial fibrillation and dementia include hypertension, type 2 diabetes, heart failure, smoking, vascular disease, sleep-related breathing disorders and advanced age. These factors lead to structural and functional changes in the brain, which in turn promote cognitive decline. Stroke, an important predictor of cognitive impairment, is directly linked to atrial fibrillation. Small cerebral hemorrhages or microbleeds also occur more frequently in people with atrial fibrillation and are associated with cognitive decline.
Reduced cardiac output associated with atrial fibrillation (similar to heart failure) can affect blood flow to key areas of the brain responsible for cognitive function. Both atrial fibrillation and Alzheimer’s disease are associated with systemic inflammation, and inflammatory biomarkers are linked to an increased risk of blood clots and brain injury. Although further research is needed to investigate this link, the observation illustrates the complex interaction between the nervous and cardiovascular systems.
Effective treatment of atrial fibrillation, including anticoagulant medication, rhythm control or catheter ablation, may reduce the risk of cognitive decline. Ongoing studies are investigating whether restoring a regular heart rhythm through catheter ablation can reduce cognitive dysfunction compared to taking medication alone.
Coronary Heart Disease
Coronary heart disease significantly increases the risk of dementia and cognitive impairment. A large systematic review of more than 1 million adults shows that people with heart disease have a 27% higher risk of developing dementia than people without heart disease. Up to 50% of people suffer a loss of brain function after a heart attack. Data from several large-scale studies show that a heart attack is associated with a greater decline in cognitive function, including memory and executive function. Increased calcium deposits in the arteries are also associated with a higher risk of developing dementia.
Coronary artery disease can affect brain function through various mechanisms. Common risk factors such as high blood pressure and type 2 diabetes cause inflammation that affects the blood-brain barrier and reduces blood flow to the brain, leading to a decline in cognitive ability and dementia. Heart disease is also associated with small vessel disease in the brain and reduced blood flow to the brain, resulting in impaired cognitive ability. These problems also occur in patients with Alzheimer’s disease, suggesting a close link between damage to the blood vessels and degeneration of the brain. In addition, genetic factors that increase the risk of heart disease can also contribute to brain shrinkage and cognitive decline. Improving vascular risk factors may preserve cognitive performance, although specific effects in patients with coronary artery disease have not been fully established. Intensive blood pressure treatment has shown promise in reducing mild cognitive impairment, but not in dementia. Other studies suggest that controlling cardiovascular risk factors through lifestyle measures such as diet and exercise may help to maintain cognitive health.
Although new drugs are being developed to treat Alzheimer’s disease, the medical community recognizes that prevention is better than cure. According to Testai, more research is needed to confirm and characterize how cardiovascular care can improve brain health. Further research is also needed to understand how gender, race and ethnicity may affect the brain-heart connection.