Cognitive Decline May Accelerate After
Ischemic Events

Debra L. Beck

June 19, 2019

After a diagnosis of myocardial infarction (MI) or angina pectoris, individuals enrolled in the English Longitudinal Study of Aging (ELSA) showed more accelerated cognitive decline than those who remained free of coronary heart disease (CHD).

The findings, published in the June 25 issue of the Journal of the American College of Cardiology, also showed that the cognitive deterioration occurred not in the immediate period after the event, but more gradually over a median follow-up of 12 years.

"Even small differences in cognitive function can result in an increased risk of dementia in the long-term," said Wuxiang Xie, PhD, in a JACC press release. Xie is the study's lead author and a research fellow at the Imperial College School of Public Health in London, United Kingdom.

ELSA is one of the largest longitudinal studies investigating the progression of cognitive decline before and after CHD diagnosis. The study is a nationally representative study of community-dwelling adults living in England.

This analysis included data from a total of 7888 stroke-free participants aged 50 and older who had a baseline and at least one follow-up reassessment of cognitive function between 2002 and 2017.

The researchers excluded individuals who had a history of stroke or MI, had a confirmed diagnosis of dementia or Alzheimer's disease at baseline, or who had an incident of stroke during follow-up.   

Participants' cognitive abilities were tested across three domains: verbal memory, semantic fluency, and temporal orientation.

Over a median of 12 years, 5.6% of participants had an MI or angina event. There were 254 MIs and 286 angina events.

When investigators compared the slope of trajectories, those with CHD showed faster rates of cognitive decline in all three tests compared with those who remained CHD-free.

Interestingly, the annual rate of decline before the CHD event did not differ compared with those who did not experience an event. This might be because the cognitive assessments used in the study were not sensitive enough, said Xie and colleagues, or could suggest that the atherosclerotic process and related hypoperfusion might be compensatory before the actual manifestation of disease such that no cognitive impairment was detectable.

Also, there was no evidence of a short-term cognitive decline after the CHD diagnosis, such as might be expected.

"This indicates that unlike brain damage caused by cerebrovascular disease (eg, stroke), the hypoxic-ischemic brain injury induced by CHD might be minor and thus insufficient to cause cognitive impairment in the short term," write Xie and colleagues.

The Slippery Slope of Cognitive Decline

"Coronary heart disease might be a critical factor for the slope of the cognitive trajectory to meet the cut-off level for clinical cognitive impairment prematurely and to simultaneously reduce the amount of cognitively vital years," write Suvi P. Rovio, PhD, and colleagues in an accompanying editorial.

Rovio and coeditorialists Katja Pahkala, PhD, and Olli T. Raitakari, MD, PhD, are all from the University of Turku in Finland.

They noted that the lack of acute cognitive decline post-CHD event offers evidence that the ischemic event as such doesn't necessarily cause acute structural alteration in the brain (eg, microinfarcts), but rather that heart disease itself might have longer-term effects on cerebrovascular function — perhaps via functioning of the blood–brain barrier and perfusion and oxidation in the brain.

"While primordial and primary prevention would be the most optimal outlooks to postpone clinical cognitive impairment, it is crucial to identify specific at-risk populations for targeted secondary and tertiary prevention," they add.

This study has several strengths and limitations. On the plus side, it's one of the largest longitudinal studies looking at the progression of cognitive decline before and after a CHD diagnosis in a stroke-free population.

Limitations include the use of self-reported doctor-diagnosed incident CHD; relatively simple measures of cognitive function; and limited information on the date of CHD diagnosis, symptom severity, acute treatments, and medications.

The 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. The authors and editorialists have disclosed no relevant financial relationships.  

J Am Coll Cardiol. Published online June 17, 2019. Full text, Editorial

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