Exploring Cognitive Concomitants of Mental Fatigue in Patients with Coronary Artery Disease

Fatigue and reduced exercise capacity are common concomitants of coronary artery disease (CAD). They are known to be associated with the deterioration in mental health, including emotional and cognitive status. However, the precise nature of the inter-relationship is poorly understood. The aim of this study was to investigate the relationship between fatigue and exercise capacity on the one hand and changes in cognitive functioning on the other, to generate new heuristics for clinical management and outcome prediction of CAD.

A cross-sectional study included 827 in-patients (58 ± 9 years, 75% men) with CAD. Patients were evaluated for demographic, cardiac characteristics, and exercise capacity. The Multidimensional Fatigue Inventory-20 was used to assess fatigue, the Mini Mental State Examination for global cognitive function, the Digit Span Test, Digit Symbol Test, and Trail Making Test for executive aspects of cognitive functioning, and the Hospital Anxiety and Depression Scale for anxiety and depression symptom severity.

Using multiple regression analysis, after adjusting for possible confounders such as anxiety and depression, mental fatigue was associated with several executive aspects of cognitive function including short-term memory (Digit Symbol Test pairs recalled correctly [β = -0.127, p < 0.005]), psychomotor performance (time to complete the Digit Symbol Test [β = 0.089, p < 0.03]), and cognitive processing speed (Trail Making Test A [β = 0.081, p < 0.05]).

In rehabilitating CAD patients, certain aspects of executive functioning were independently associated with mental fatigue. These findings suggest that the subjective experience of mental fatigue, rather than reduced exercise capacity, is significantly associated with cognitive function.