new research suggests.
Although cognition in the acute phase after MI was not different than those without an MI in large observational cohorts, cognitive decline became significantly different over a median 6.5 years of follow-up.
The results reinforce the idea that heart health is closely tied to brain health, lead study author Michelle C. Johansen, MD, PhD, assistant professor of neurology cerebrovascular division, Johns Hopkins University, Baltimore, said in an interview. “From a clinical standpoint, heart health affects brain health and there may be effective interventions to prevent heart attack from happening that could reduce the rate of cognitive decline.”
The study was presented during the International Stroke Conference sponsored by the American Heart Association.
Researchers are increasingly recognizing the vascular contribution to cognitive impairment, said Dr. Johansen. This could involve “silent” or subclinical strokes that go unrecognized until seen on imaging.
The study included 31,377 adults free of MI and dementia from six large, well-known cohort studies: the Atherosclerosis Risk in Communities Study, the Coronary Artery Risk Development in Young Adults Study, the Cardiovascular Health Study, the Framingham Offspring Study, the Multi-Ethnic Study of Atherosclerosis, and the Northern Manhattan Study
About 56% of study participants were women, 23% were Black, 8% were Hispanic, and 69% were White.
They were followed from 1971 to 2017 with investigators repeatedly measuring vascular risk factors. The median study follow-up was 6.5 years, but some were followed for up to 20 years. During that time, there were 1,047 incident MIs.
The researchers performed a pooled analysis from these studies “using some fancy statistical techniques,” said Dr. Johansen. “The unique thing about this study was we were able to harmonize the cognitive measures.”
This allowed the researchers to determine if incident MI affected cognitive decline soon after the event and then long-term after the event. The primary outcome was change in global cognition. Additional outcomes were memory and executive function.
The median time between the first MI and the cognitive assessment was about 1.8 years but ranged from about 6 months to 4 years, said Dr. Johansen. Participants were a median age of 60 years at the time of the first cognitive assessment.
The researchers adjusted results for demographic factors, heart disease risk factors, and cognitive test results prior to the MI. Participants who had a stroke during the follow-up period were excluded from the analysis as stroke can affect cognition.
The study showed incident MI was associated with significant decline in global cognition (–0.71; 95% confidence interval, –1.02 to 0.42; P < .0001) and executive function (–0.68; 95% CI, –0.97 to 0.39; P < .004), but not memory, after the MI.
As cognition naturally declines with age, the researchers took that into consideration. “We anticipated cognition over time was going to go down, which it did, but the question we asked was: ‘How did the slope, which we knew was going to decline over time, compare in people who did not have a MI versus those that did?’ ” said Dr. Johansen.
After adjusting the model accordingly, the effect estimates indicating declines in global cognition and executive function were not significant.
However, another model that looked at the effect of incident MI on decline in cognitive function over the years following the event found significant differences.
Compared with participants without MI, those with incident MI had significantly faster declines in global cognition (–0.15 points/year faster, 95% CI, –0.21 to –0.10; P < .002), memory (–0.13 points/year faster, 95% CI, –0.23 to –0.04; P = .004), and executive function (–0.14 points/year faster, 95% CI, –0.20 to –0.08; P < .0001).
Dr. Johansen surmised that MI may result in subclinical infarcts or inflammation, or that MI and cognitive decline have shared vascular risk factors.
She said she can only speculate about why there was not more of a cognitive decline surrounding the MI. “It may be that right after the event, subjects are kind of sick from other things so it’s hard to see exactly what’s going on. Sometimes people can have other problems just from being in the hospital and having a heart attack may make cognition difficult to assess.”
The researchers also looked at those who had a second MI. “We asked whether the decline we saw after the first heart attack among those who had two heart attacks was explained by the fact they had more than one heart attack, and the answer to that question is no,” Dr. Johansen said.
The next research steps for Dr. Johansen and associates are to look at differences in race and sex.
Karen L. Furie, MD, chair, department of neurology, Brown University, and chief of neurology at Rhode Island Hospital, the Miriam Hospital, and the Bradley Hospital, all in Providence, provided a comment on the research.
MI and cognitive decline have a number of common risk factors, including hypertension, diabetes, high cholesterol, smoking, physical inactivity, and poor diet that can lead to obesity, said Dr. Furie.
“It’s critically important to identify these risk factors as early as possible,” she said. “People in early and middle life may not be receiving optimal medical management or engaging in ideal lifestyle choices and these contribute to the development and progression of atherosclerotic disease over the subsequent decades.”
In theory, she said, if these risk factors were eliminated or adequately treated earlier in life, “both the heart and brain could age naturally and in a healthy manner, enabling a higher functioning and better quality of life.”
The study was funded by the National Institute of Neurological Disorders and Stroke and the National Institute of Aging of the National Institutes of Health. Dr. Johansen receives research funding from NINDS.
A version of this article first appeared on Medscape.com.