Higher risk of dementia after a heart attack

4 minute read

Myocardial infarction increases the risk of cognitive decline and dementia, according to a major US study.

Having a heart attack increases the risk of cognitive decline and dementia in the years afterwards, new research suggests.

Preventing myocardial infarction may be important for long-term brain health, according to a meta-analysis of six major US epidemiological cohort studies over nearly 50 years.

In over 30,000 adults, more than 1000 had had at least one heart attack over the study duration. And these 1000 people had faster decline in global cognition, memory and executive function over an average of six years after the MI compared with those who did not have a cardiovascular event.

“Discussion of the potential cognitive ramifications of MI should be considered as a potential motivator when counselling patients at risk for MI,” the researchers wrote in JAMA Neurology.

“Additionally, individuals who have experienced an MI should be followed up for accelerated cognitive decline in the years after MI. The findings also suggest that prevention of MI may be a strategy to preserve brain health in older adults.”

The researchers also found differences in cognitive decline between men and women.

“Females had less of a decline in global cognition than males but more of a decline in executive function than males.

“There has been other evidence of differential decline across cognitive domains by sex, but our results may also suggest a nonbiological reason that may be related to the cognitive measures themselves, and therefore these findings merit confirmation.”

Commenting on the study, dementia researcher Professor Kaarin Anstey said the paper built on previous research showing that heart conditions were risk factors for late-life dementia.

Preventing myocardial infarction may be a strategy to preserve brain health, said Professor Anstey, senior principal research scientist at NeuRA and director of the UNSW Ageing Futures Institute.

“GPs need to be aware that myocardial infarction increases the risk of cognitive decline and dementia. This should motivate risk reduction such as optimal management of vascular risk factors and recommending protective lifestyle behaviours such as physical activity and healthy diet.”

Professor Anstey noted that the cognitive changes reported in the study were small over one year.

“For example, those who experienced MI declined by 0.13 points on average on a memory test in one year, which would not be detectable in a clinical assessment. Of course, there may be some who declined more or less than this.

“But the key point about prevention of late-life dementia and cognitive impairment is that these effects accumulate over decades, so this small effect may add up to a significant loss of cognitive function over time.”

Professor Anstey said whether this led to decline in cognitive symptoms and impairment in daily activities would depend on each individual’s prior level of cognitive abilities, their overall health and their overall risk factor profile including genetic risk.

“What is interesting about the results is that there were few immediate impacts on cognition, but the people who had an MI subsequently declined faster than those who had not had an MI.

“The vascular changes that caused the MI may also impact blood vessels in the brain, or the MI itself may have some impact on cerebral blood flow which may in turn lead to faster cognitive decline.”

In an accompanying editorial, US neurologists noted the study – and previous studies like it – could not explain the reason for acceleration in cognitive decline after myocardial infarction.

“It seems unlikely that immediate consequences of myocardial tissue injury are the explanation for the post-MI decline found in the study.” 

Acute infarction with left ventricular dysfunction could cause cerebral hypoperfusion, but that would cause an immediate drop in cognitive test scores, not a slow progressive decline, they said.

“The lack of an immediate decrease in cognition and the steeper decline in subsequent years suggests that the MI was associated with a slower, progressive process that accelerated cognitive decline, rather than an acute process.”

The association may be due to “progressive cardiac dysfunction due to ischaemic cardiomyopathy, with alterations in blood pressure and cardiac output leading to brain ischaemia”.

Patients may also be vulnerable to atrial fibrillation after myocardial infarction, or may have chronic inflammation, they said. 

“Even though the mechanism for post-MI cognitive decline is unclear, the risk seems real. There are steps the clinician can take to improve outcomes even without full knowledge of the mechanisms.

“Patients with history of MI should be asked about cognitive symptoms periodically, with follow-up cognitive screening for patients in whom symptoms are endorsed by themselves or an informant.”

JAMA Neurology 2023, online 30 May

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