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Can ‘silent’ heart attacks pose a risk to brain health? Image credit: Iuliia Burmistrova/Getty Images
  • Cardiovascular disease is a major risk factor for cognitive decline and dementia.
  • Research has linked heart attacks with an increased risk of cognitive decline.
  • Now, a study suggests that even undiagnosed heart attacks, or silent myocardial infarctions, can speed cognitive decline.
  • The researchers recommend that routine electrocardiograms to detect silent MIs, together with self-reported history, might help identify individuals at higher risk of long-term cognitive impairment.

Cardiovascular disease is a group of disorders of the heart and blood vessels, thought to affect around 650 million people worldwide. A common result of cardiovascular disease is myocardial infarction, better known as a heart attack.

In the United States, the Centers for Disease Control and Prevention (CDC) report that about 805,000 people have a heart attack each year, of which one in five are “silent,” or undiagnosed at the time.

Now, a study has suggested that any type of heart attack, even a silent one, increases a person’s risk of cognitive decline over time.

Speaking to Medical News TodayCheng-Han Chen, MD, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, explained that:

“It is not entirely understood why a history of myocardial infarction is associated with faster cognitive decline. It may be that people who have heart attacks are also more likely to develop blockages in blood vessels in the brain, leading to brain ischemia and even brain infarcts that accelerate brain deficits.”

The research, which is published in strokesuggests that electrocardiograms (ECG), and self-reported history, could be a low-cost way to identify people at higher risk of cognitive decline.

Cardiovascular disease linked to cognitive decline

Research has suggested that there is a link between cardiovascular disease and cognitive decline, and that the link is two-way.

Coronary heart disease, heart failure, higher blood pressure variability, sudden blood pressure drops, and atrial fibrillation are all thought to increase the likelihood of cognitive impairment. But cognitive impairment also increases the risk of cardiovascular events, such as strokes and heart attacks.

This new research looked at data from more than 20,000 Black and white Americans aged 45 and over enrolled in the REGARDS (REAsons for Geographic And Racial Differences in Stroke) study, a longitudinal cohort study investigating elevated stroke mortality in the south eastern United States.

This region, known as the Stroke Belthas had a higher stroke mortality rate than the rest of the US since the 1940s, for reasons which may include a larger proportion of Black people and residents with higher prevalence of traditional stroke risk factors, higher prevalence of inflammation and infection, and lower socioeconomic status.

For their analysis, researchers included participants who had baseline interview data about their medical history, had undergone height, weight, blood pressure, ECG, medication inventory, fasting blood sample, and urine collection at baseline and follow up and had interpretable ECG data.

In their interview, participants were asked whether they had ever had a heart attack diagnosed by a doctor. They then underwent ECG screening, which detected signs of a previous heart attack.

The researchers recorded silent heart attacks for those people who had ECG evidence of a previous heart attack, but had never been diagnosed with one. Those who had no ECG evidence of heart attack, but had been diagnosed with one were recorded as “self-reported myocardial infarction.”

In total, 2,183 (10.4%) of participants had any heart attack, of which 1,098 were self-reported (5.2%), 281 clinical (1.3%), and 804 silent heart attacks (3.8%).

During the follow-up period of between 10 and 14 years, the researchers also carried out annual cognitive assessments with all participants, to assess whether they had any cognitive impairment over time.

Any heart attack linked to faster cognitive decline

The researchers found that any heart attack, whether silent, self-diagnosed, or with evidence from ECG and diagnosis, was linked to higher likelihood of cognitive impairment, with an even stronger link to severe cognitive impairment over time.

White, Black and male participants all showed similar declines in cognitive scores for all MI types. For females, only self-reported and silent heart decline attacks were associated with faster cognitive, but the researchers noted that silent MI was more common in females. They suggest that this may be due to under diagnosis of MI in females.

The researchers noted that individuals with silent heart attacks have more small vessel disease, and less large vessel atherosclerosis that those with recognized heart attacks, as well as greater risk of ischemic stroke.

They suggest that subclinical cerebral infarcts — small strokes that cause no symptoms and often precede symptomatic strokes — in these people could contribute to cognitive deterioration.

Could routine ECG help detect those at most risk?

ECG, which Chen — who was not involved in the recent research — confirmed was “a useful screening tool for patients we think are at higher risk of heart disease,” detects undiagnosed heart attacks by recording irregular heart patterns.

In people who have had a heart attack, the Q-wave — the small wave before the main contraction of the ventricles that results in a large R-wave on the ECG readout — is deeper or wider than on an ECG from someone who has not had a previous heart attack.

The researchers conclude that: “evidence of a prior (myocardial infarction) was associated with an accelerated rate of cognitive decline in a large national, biracial population,” and “(u)sing ECG and self-reported history may provide a pragmatic, low-cost strategy to identify individuals at elevated risk for cognitive decline.”

Keep heart and blood vessels healthy to reduce cognitive decline risk

Studies show that common cardiovascular diseases interact with cognition, particularly in the elderly, and that they may increase the risk of dementia. Keeping your heart and blood vessels healthy could, therefore, help reduce your likelihood of cognitive decline.

Chen advised:

“To keep the blood vessels in the heart and brain healthy, we recommend that people get regular physical activity, eat a diet low in saturated fat and sodium, avoid tobacco and alcohol, keep their blood pressure, blood sugar, and cholesterol numbers under control, maintain a healthy weight, and get enough quality sleep.”