Everyone’s brain ages as the years pass, some more than others. What’s considered normal is typically quite subtle: Processing speed slows, the ability to pay attention declines, and it can be common to have trouble finding the right word. However, age-related cognitive decline is quite different from Alzheimer’s disease and other dementias and should not be confused with those, experts say.
In the new study, published Tuesday in the journal JAMA Neurology, researchers analyzed data from six major studies on heart disease and cognition conducted between 1971 and 2019 in the United States. None of the 30,465 people chosen for those studies had dementia or experienced a heart attack or stroke before the study started, and all underwent at least one cognitive assessment.
During the course of the research, however, over 1,000 of the participants had an acute myocardial infarction, or heart attack. No immediate change in cognition was seen, but the cognitive scores of those who had a heart attack accelerated over the next six or so years at a much steeper rate than that of their peers who did not have a heart attack.
The increase in the annual rate of decline for people who had heart attacks was small, wrote Dr. Eric Smith and Dr. Lisa Silbert in an accompanying editorial. Smith is the medical director of the Cognitive Neurosciences Clinic at the University of Calgary in Alberta, and Silbert is a professor of neurology at Oregon Health & Science University School of Medicine in Portland.
However, “it is possible that accruing subclinical decline over years or decades could eventually impair function or decrease cognitive reserve, making the person more vulnerable to the effects of age-related neurodegenerative pathologies,” Smith and Silbert wrote.
The steepest annual rate of decline after heart attack was seen in White compared with Black individuals and in men compared with women, the study found, and could not be explained by stroke or new atrial fibrillation — an irregular, often rapid heart rhythm that can lead to blood clots in the heart.
Past studies found link
This isn’t the first study to find a connection between accelerated cognitive decline and heart attacks, Smith and Silbert noted.
“An acceleration in the annual rate of cognitive decline after MI (myocardial infarction) was also seen in 7888 participants in the English Longitudinal Study on Aging, of whom 254 had an MI and 286 had angina during up to 12 years of follow-up,” they wrote.
As in the new study, people with heart attacks or angina (chest pain) had annual rates of cognitive decline before the attack similar to those of people who never had a heart attack, but then experienced accelerated cognitive decline, they added.
However, the exact mechanisms that might drive a drop in cognition are not yet clear, Smith and Silbert noted.
“Stroke was excluded as the cause of the decline,” they wrote, adding that injury to the heart tissue after an attack appeared unlikely.
“The lack of an immediate decrease in cognition and the steeper decline in subsequent years suggests that the heart attack was associated with a slower, progressive process that accelerated cognitive decline,” they wrote.
Possible explanations may include depression after having a heart attack, which has been linked to dementia, they said. Chronic inflammation, blood pressure abnormalities and small blood vessel disease, which are also linked to dementia, may be contributing causes as well, they said.
“Even though the mechanism for post-MI cognitive decline is unclear, the risk seems real,” Smith and Silbert wrote. “Patients with history of MI should be asked about cognitive symptoms periodically, with follow-up cognitive screening … referral to a cognitive specialist or neuropsychologist may be warranted in select cases.”