Mechanisms associated with cognitive impairment and mood in elderly heart failure patients

Cognitive impairment is a prevalent comorbidity seen in elderly heart failure (HF) patients and is linked to poor quality of life, reduced self-care abilities and increased hospital readmissions, possibly due to a reduced capacity to understand and follow complex treatment protocols. In addition to cognitive impairments, HF patients also endure depressed mood and increased anxiety. In order to establish the most effective treatment for improving or ameliorating cognitive impairment and mood in older HF patients, a better understanding of the basic physiological mechanisms is necessary. Previous research suggests that mechanisms underlying cognitive impairments in these patients include reduced cerebral blood flow but little is known about the influence of other processes on their cognitive impairments. The aim of the present thesis was to examine whether inflammatory, antioxidant, oxidative stress and arterial stiffness explain cognitive deficits and depressed mood and anxiety in elderly HF. A further aim was to explore additional cognitive domains that may be impaired in HF using a well-validated computerised neuropsychological assessment battery. In this thesis, 36 patients with HF (NYHA class II, III or IV) aged 60 years and above were compared to 40 age- and sex- matched controls on tests of cognitive function, mood and several biological mechanisms including cerebral blood flow, arterial stiffness, inflammation, oxidative stress and antioxidant markers. The results indicated that Power of Attention is an additional cognitive domain impaired in elderly HF patients. Determinable reactive oxygen metabolites (DROMs) are significantly elevated in HF compared to controls. Furthermore, the results indicated that reduced common carotid arterial blood flow velocity, arterial stiffness and reduced coenzyme Q10 levels were related to poor attention and psychomotor abilities in elderly HF patients. Common carotid arterial blood flow velocity and reduced circulating coenzyme Q10 were associated with reduced executive function in HF. Although inflammation and oxidative stress were significantly elevated in the HF group, there was no indication these biomarkers were related to cognitive function. Finally, the results indicated that cerebral blood flow, arterial stiffness, antioxidants and inflammatory makers did not relate to depression or anxiety levels in HF. In conclusion, this thesis confirmed the existence of cognitive impairments in HF, and suggested that Power of Attention may be a further, previously undescribed impairment. These findings also indicate that DROMs are a useful measure of oxidative stress in older HF patients, and those interventions that reduce central pulse pressure, increase cerebral blood flow and elevate coenzyme Q10 levels may improve attention and executive function in elderly HF patients.