Ischemic Events Worsen Long-term Cognitive Decline

Future research is needed to elucidate the mechanisms by which CHD affects cognition, and whether that’s causative, experts say.

Ischemic Events Worsen Long-term Cognitive Decline

Coronary heart disease (CHD) can lead to a faster decline in long-term cognition after—but not before—ischemic events, according to new data.

Prior studies have linked hypertension and congenital heart disease with cognitive decline, but evidence on the effects of CHD on cognition has been inconsistent.

“Although making comparisons with previous studies is difficult given the discrepancies in the definition and severity of CHD, the cognitive function tests used, outcome measurements, and length of follow-up, our present finding is, in general, consistent with a previous study reporting that incident cardiovascular disease is associated with worse cognitive performance, including memory and information processing, but not executive function,” write Wuxiang Xie, PhD (Peking University Health Science Center, Beijing, China), and colleagues.

“It is still too early to conclude what kind of change should be done,” Xie told TCTMD in an email. “For now, careful monitoring of cognitive function [in] CHD patients and early intervention to preserve cognitive function might be a good start.”

CHD Increases Cognitive Decline

For the study, published in the June 25, 2019, issue of the Journal of the American College of Cardiology, the researchers analyzed 7,888 participants of the English Longitudinal Study of Ageing who had no history of stroke or incident stroke during a median follow-up of 12 years. All underwent a cognitive assessment at baseline (2002-2003) and again at some point between 2004 and 2017.

Over the study period, there were 480 incident CHD events, amounting to a rate of 5.6%. On multivariate analysis, the rates of decline in global cognition (-0.018 Z score/year; 95% CI -0.029 to -0.007), verbal memory (-0.015 Z score/year; 95% CI -0.023 to -0.008), sematic fluency (-0.011 Z score/year; 95% CI -0.019 to -0.003), and temporal orientation (-0.015 Z score/year; 95% CI -0.027 to -0.003) were higher among those who experienced an event than among those who did not, regardless of sex. Interestingly, the annual rate of cognitive decline prior to a diagnosis of CHD was similar to that of people never diagnosed with CHD, and there did not appear to be any effect of CHD on short-term cognitive decline.

“We were pretty surprised by the result that incident CHD was associated with accelerated cognitive decline after, but not before, the event,” Xie said. “Our preliminary hypothesis was that the long-term exposure to vascular risk factors might contribute to cognitive decline, and so that the decline must have started before incident CHD. However, we did not find any significant decline before the event, which was consistent with the findings of the Maastricht Aging Study. Therefore, we think incident CHD might play a role in triggering faster cognitive decline.”

Untangling the Mechanisms at Play

In an editorial accompanying the study, Suvi P. Rovio, PhD (University of Turku and Turku University Hospital, Finland), and colleagues write that the short-term results are notable especially “given that previous research has often supported the hypothesis that the link between cardiovascular health and cognitive function is via cerebrovascular-related structural brain damage, which manifests as acute cognitive impairment and/or accelerated short-term cognitive decline.”

However, it seems that a coronary heart disease event “does not necessarily cause acute structural alterations in the brain (eg, microinfarcts), but that the incident coronary heart disease might act more via longer-term alterations affecting the cerebral vascular function (eg, the function of the blood-brain barrier as well as perfusion and oxidation in the brain),” they add.

The editorialists also take interest with the study’s inability to find any acceleration in cognitive decline prior to an ischemic event, writing that while clinical cognitive impairment thought to be preceded by subclinical deficiencies “years or even decades before they become clinically detectable,” the CHD patients in this study also had higher levels of CV risk factors throughout follow-up, “which could be hypothesized to have caused subtle alterations in cognitive function.”

It is possible that “there actually are subtle differences in the cognitive functions that have remained undetectable due to methodological limitations,” they add. “This highlights the need for wider discussion on the used cognitive measurement methods not only in a scientific, but also in a clinical context.”

“Taken together, the present findings suggest that careful monitoring for cognitive dysfunction in participants with CHD diagnosis are warranted in the years following their diagnosis,” Xie and colleagues write, adding that the mechanisms by which CHD may affect cognition remain to be elucidated.

“Even if preventing the occurrence of risk factors (ie, primordial prevention) or lowering established risk factor levels (ie, primary prevention) would be the most optimal options to prevent or postpone the clinical cognitive impairment, it is crucial to identify specific at-risk populations for targeted secondary and tertiary prevention,” the editorialists conclude. “Given that the found associations are causal, the present results suggest that interventions targeted at risk factors for coronary heart disease would additionally not only target the risk factors for cognitive decline, but also the possible trigger affecting the slope of cognitive trajectory (ie, coronary heart disease).”

Sources
Disclosures
  • This study was funded by the National Natural Science Foundation of China, the Beijing Natural Science Foundation, and the Newton International Fellowship from the Academy of Medical Sciences.
  • Xie and Rovio report no relevant conflicts of interest.

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