Patients with stable coronary heart disease (CHD)—despite being considered “fit” and participating in phase III cardiac rehabilitation—demonstrated worse cognitive function when compared to healthy, age-matched individuals in a single-center study published in PLOS One.

Researchers from the Montreal Heart Institute and University of Montreal studied 25 patients with stable CHD compared to 20 age-matched, healthy controls and 22 young healthy controls. They performed a battery of written and verbal tests to measure resting cognitive function and an incremental exercise test on a stationary bike to measure cardiopulmonary function.

“Our data would indicate that regular physical activity and high fitness level are insufficient to prevent the ‘step-down’ in cognitive function that occurs from healthy age-matched controls to older patients with CHD,” wrote lead researcher Mathieu Gayda, PhD, and colleagues. “One explanation for this persistence difference could include irreversible vascular changes whereby exercise is no longer able to exert its beneficial effects on the cerebral vasculature. Other potential explanations include a higher prevalence of irreversible brain lesions in patients with CHD such as white matter lesions, brain infarcts and brain atrophy, which also would not be expected to respond to exercise training.”

The mean ages of the study groups were 70 for patients with CHD, 67 for old healthy controls and 33 for young healthy controls. More than two-thirds of each group was male, so the authors cautioned the results may not be generalizable to women.

The younger group scored the best on measurements of short-term and working memory, processing speed, cognitive inhibition and flexibility and long-term verbal memory. The older control group scored the second-best in all categories, followed by the patients with CHD.

Exercise testing revealed maximal aerobic capacity, maximal cardiac output and cerebral oxygenation and perfusion were related to resting cognitive function.

“While the aging process itself is associated with reduced cognitive function, based upon our results, it is unclear what role reduced cerebral oxygenation/perfusion and cardiopulmonary and hemodynamic responses play in explaining the impairments in cognitive function we observed in our fit CHD cohort,” the researchers wrote. “Larger studies using several imaging modalities for evaluating cerebral blood flow and oxygenation/perfusion are required to better understand the potential role of cerebrovascular and neurovascular function in explaining the cognitive impairments we observed in our two aged cohorts.”