A hidden heart attack may leave more than cardiac damage behind. Researchers found that even silent myocardial infarctions were linked to faster cognitive decline over time, raising new questions about how heart health shapes long-term brain function.
Study: Prior Myocardial Infarction and Cognitive Decline: The REGARDS Cohort. Image credit: PeopleImages/Shutterstock.com
A recent study published in the journal Stroke found that people with a self-reported history or electrocardiogram (ECG) evidence of a previous myocardial infarction experienced a faster decline in global cognitive function.
Hidden cardiovascular risks and brain health
Vascular disease is a major and potentially modifiable risk factor for cognitive impairment and dementia. Previous studies have linked acute myocardial infarction (AMI), commonly known as a heart attack, with an increased risk of long-term cognitive decline.
In clinical practice, prior MI is often identified using a patient’s self-reported medical history or electrocardiogram (ECG) findings such as Q-waves. However, it remains unclear whether these routinely used measures can reliably identify people at higher risk of future cognitive decline.
An estimated 22 %-44 % of myocardial infarctions are never clinically diagnosed but leave characteristic Q-wave patterns on ECG, a condition known as silent MI. Despite the absence of recognized symptoms, silent MI has been associated with a higher risk of dementia, white matter disease, and silent brain infarcts. Previous evidence for this association was largely limited to studies of elderly men, highlighting the need for validation in more diverse populations.
To investigate this question, the researchers used data from the REGARDS cohort, a large prospective U.S. study designed to examine vascular contributors to brain health. The cohort includes detailed cardiovascular assessments alongside standardized cognitive testing repeated over many years.
Using these data, the researchers examined whether self-reported or ECG-detected evidence of prior MI was associated with more rapid cognitive decline in a diverse population of Black and White American adults.
Examining cognitive decline in association with MI history
In the current study, REGARDS participants were stratified into four subgroups:
- Non-MI: no self-reported history or ECG evidence of MI
- Self-reported MI: the patient reported a physician diagnosis of MI, but no ECG evidence was found
- Clinical MI: the patient had a history of MI, and the ECG showed a Q-wave
- Silent MI: patient did not report any MI history, but the ECG showed a Q-wave
Global cognitive function was assessed by a telephone-based screening. The scores were followed over time, and the change was examined for association with prior MI.
Cognitive decline with prior MI
The baseline cohort included 20,923 individuals, with a median follow-up of 10.1 years. Over this period, 4,884 participants died, about 23 %. The mortality rate in the prior MI subgroup was 44.4 %, compared with 21 % in the non-MI subgroup.
At baseline, there were 2,183 participants with a history of prior MI. Of these, 1,098 had a self-reported history of prior MI, 281 had clinical MI, and 804 had silent MI. Participants with prior MI were more likely to have cardiovascular risk factors.
The odds of developing cognitive impairment per year were slightly increased by 4 %-9 % in participants with MI across all subcategories. Severe cognitive impairment was also more likely among participants with any MI, silent MI, and self-reported MI, whereas clinical MI showed a similar trend that was not statistically significant.
The researchers found that prior MI was associated with a faster annual decline in cognitive function of 0.016 points on the study’s global cognitive scale compared with patients without prior MI. Similar rates of accelerated decline were observed across all MI subcategories, including self-reported MI (0.016 points annually), clinical MI (0.020 points annually), and silent MI (0.015 points annually). Although numerically small, these differences could accumulate over time.
Accelerated cognitive decline was observed in both Black and White MI participants and both sexes. Among women, silent and self-reported MI were associated with accelerated global cognitive decline, whereas for men, all subtypes showed this association. Clinical MI in women showed a similar direction of association, but this did not reach statistical significance.
Association with domain-specific cognitive decline
The specific areas of cognitive impairment tested here included executive function (mental skills required to plan, organize, pay attention, regulate impulses, solve problems, and adapt to new demands), learning, and memory.
Participants with self-reported MI showed a faster decline in all these domains, whereas the clinical MI group showed significant decline only in memory. Silent MI was not linked to a decline in any of these domains. The authors noted that these domain-specific findings should be considered exploratory, given the smaller sample size and the infrequent administration of these assessments.
Shared vascular damage may drive brain decline
These findings agree with the increased risk of cognitive impairment and of dementia among individuals with coronary ischemia, as reported by prior studies. The mechanisms underlying this association remain hypothetical.
For instance, both have common risk factors; however, after adjusting for new-onset cardiovascular events, the risk of cognitive decline continued to be accelerated. Other possibilities include silent infarcts in the brain, reduced clearance of waste products from brain tissue, microvascular disease, poor cerebral perfusion, and systemic inflammation.
The variable patterns of decline across cognitive domains with MI subtype may reflect different underlying mechanisms of cognitive deterioration despite a common atherosclerotic origin.
Silent MI and cognitive decline
An important finding of this study is the association between accelerated cognitive decline and silent MI, an often-overlooked subgroup in prior population-based studies. This could have contributed to inconsistent results in earlier research. Notably, nearly 37 % of MI participants in the REGARDS cohort at baseline belonged to this subcategory.
The authors suggest that “silent MI may represent a cardiac manifestation of broader systemic microvascular disease.” Individuals with silent MI are less likely to have large vessel atherosclerosis and more likely to have widespread small vessel disease. This agrees with earlier findings that this subgroup is at higher risk of ischemic stroke, perhaps because of repeated silent cerebral infarcts.
Brief cognitive screening may miss subtle decline
The authors note several limitations of the study. Since biological age does not always correlate with chronological age, they might have underestimated the effect of age on cognition in participants with prior MI. The increased mortality in the MI group might have reduced the observable effect of prior MI on cognitive impairment.
The ECG criteria for MI used here are not consistent across studies, limiting their generalizability. Self-reported history of MI is of moderate sensitivity when compared with medical records. The cognitive screening tool used here is not a comprehensive assessment, may miss small changes in cognition, and is nonspecific across dementia subtypes.
Routine ECGs may identify future cognitive risk
This is among the earliest studies to explore the association between different forms of prior MI and future cognitive impairment. Overall, cognitive function declined faster in patients with prior MI, irrespective of whether it was clinically recognized or silent.
The use of simple, clinically feasible tools to identify these individuals is an important benefit supporting further research to validate these results.
The findings support further study of whether routine screening for MI via ECG and self-reported history could help identify individuals at higher risk of long-term cognitive impairment.
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