Based on data collected over nearly five decades, a new study highlights the connection between heart health and brain function.
As we age, our bodies and brains naturally become less agile. Experiencing occasional forgetfulness or taking longer to remember names or events is a normal part of the aging process. However, in some cases, cognitive decline can occur at a faster rate. Recent research suggests that individuals who have experienced a heart attack may be more prone to accelerated cognitive decline (refer to "Cognitive changes after a heart attack").
Cognitive abilities, such as reasoning and memory, can be assessed through various methods. The study in question focused on overall cognition, which includes learning, processing speed, and executive function (the ability to carry out mental tasks like planning and remembering instructions). Immediately following a heart attack, survivors did not display any noticeable cognitive changes. However, over the subsequent years, they exhibited a persistent and accelerated decline in overall cognition compared to those who hadn't experienced heart attacks. According to the researchers, this decline was equivalent to approximately six to thirteen years of normal cognitive aging.
The study aimed to gain a deeper understanding of the causes of cognitive issues and explore potential prevention strategies. To achieve this, researchers analyzed data from six large studies conducted in the United States over the past five decades. The key findings, published in the July 2023 edition of JAMA Neurology, are summarized below.
Participants: 30,465 adults without a history of heart attack, stroke, or dementia. Of these, 56% were women, 29% were Black, and 8% were Hispanic.
Study Duration: The studies were conducted between 1971 and 2019.
Occurrences: During the follow-up periods, which ranged from around five to twenty years, 1,033 individuals experienced a heart attack, with 137 of them having two heart attacks. All participants underwent at least one cognitive assessment, and those who had a heart attack received assessments both before and after the event.
Key Findings: Cognitive changes were not immediately apparent after a heart attack. However, heart attack survivors experienced a decline in cognitive ability at a faster rate than normal in the subsequent years.
So, what could explain these findings? Heart attacks may lead to changes that directly affect blood flow to the brain or trigger atrial fibrillation, a heart rhythm disorder associated with an increased risk of major strokes. These strokes can then cause severe cognitive problems that impact daily functioning, potentially leading to dementia. Additionally, individuals who have experienced heart attacks often have higher rates of depression, which is also linked to dementia.
Furthermore, the factors responsible for narrowed heart arteries, the primary cause of most heart attacks, can also contribute to cerebral small vessel disease. This condition, also known as microvascular ischemic disease, occurs due to high cholesterol levels and the constant impact of high blood pressure on the brain's small arteries. Over time, the linings of these vessels thicken, restricting blood flow and resulting in tiny "silent" strokes.
Dr. Andrew Budson, Chief of Cognitive and Behavioral Neurology at the VA Boston Healthcare System and a lecturer in neurology at Harvard Medical School, explains that a single microscopic stroke may not be visible on a brain scan. However, when multiple strokes accumulate, they become visible as bright areas on an MRI scan. These bright spots, referred to as white matter lesions, consist of bundles of nerve fibers that connect brain cells.
In recent years, medical professionals have come to realize that cerebral small vessel disease is responsible for the majority of cases of vascular dementia, which is dementia caused by blood vessel problems rather than Alzheimer's disease. Previously, vascular dementia was primarily attributed to strokes in large vessels, occurring when a clot blocks a brain artery.
In fact, brain scans of most older individuals show some evidence of white matter lesions, which are recognized as markers of the typical cognitive changes that accompany aging. However, individuals who have experienced heart attacks likely have more risk factors for small strokes, some of which may not have been identified yet. Consequently, they tend to have more white matter lesions and experience more pronounced cognitive decline. Dr. Budson, having reviewed countless brain scans, believes this is the most plausible explanation.
Adhering to a healthy diet, engaging in regular exercise, and maintaining a normal weight are already well-established measures for preventing heart attacks. Considering the added benefit of protecting brain health should further motivate individuals to prioritize these practices.
