ReviewCognitive impairment and cardiovascular diseases in the elderly. A heart–brain continuum hypothesis
Introduction
Cardiovascular diseases (CVD) including hypertension, coronary artery disease (CAD), atrial fibrillation and chronic heart failure (CHF) are highly prevalent in the elderly (Aronow, 2002). Moreover, CVDs are strongly related to cognitive impairment and dementia (Kerola et al., 2011, Eggermont et al., 2012). Although the etiology of cognitive changes in CVD disease remains unknown, the main mechanism of this relationship seems to involve embolic stroke or chronic cerebral hypoperfusion (Kalaria, 2012). Of course, cognitive impairment and dementia reduce the ability to manage the care of a complex chronic illness and reduced medication adherence (Insel et al., 2006). Interestingly, CVDs are capable of producing both Alzheimer's disease (AD) (de la Torre, 2002) and vascular dementia (VaD) (Román, 2002), the most common forms of dementia in the elderly.
We used MEDLINE, the National Research Register, Embase (1980–2006, OVID online) to search for studies that investigated the relationship between CVD and cognition, and which were published until May 2013. The search included the following key words: cardiovascular diseases; hypertension; heart failure; coronary artery disease; atrial fibrillation; cognitive impairment, dysfunction, deficit; neuropsychological functions; dementia, Alzheimer's disease, vascular dementia.
Section snippets
Cognitive function and cognitive impairment
Cognitive function involves various specific aspects referring to memory, attention, executive functioning, psychomotor speed, language, and visuo-spatial ability and it is a critical function for the consciousness of situation, needs, and goals (Borson, 2010). The Mini-Mental State Examination (MMSE) has been used as a screening measure for global cognitive performance in several studies studying the relationship between CVD and cognitive impairment (Vogels et al., 2007a, Vogels et al., 2007b
Hypertension and cognitive impairment
Among people aged 65 years and over, the prevalence is estimated to be around 8% for dementia and 65% for hypertension (Qiu et al., 2005, Kearney et al., 2005). Moreover, hypertension represents the major risk factor for vascular dementia although vascular factors may be also involved in Alzheimer dementia (Launer, 2002, de la Torre, 2002). Thus, mixed vascular and neurodegenerative dementia has emerged as the leading cause of age-related cognitive impairment (Iadecola, 2013).
CAD and cognitive impairment
The aging of the population will result in a sizeable increase in CAD incidence, prevalence, mortality, and costs (Odden et al., 2011). Over time, Coronary Artery By-pass Grafting (CABG) has been a commonly prescribed cardiac procedure for CAD patients. Unfortunately, stroke is estimated to occur in 2–6% and encephalopathy in up to ∼13% following CABG predisposing elderly CAD patients to cognitive impairment (Caplan, 2009).
Atrial fibrillation and cognitive impairment
Atrial fibrillation is an arrhythmia with high prevalence in geriatric age; approximately 10% of subjects older than 65 years and 5% of subjects older than 80 years old suffer from such arrhythmia (Aronow, 2002, Chatap et al., 2002). The high prevalence atrial fibrillation comes from the frequent association with heart disease that characterize the elderly, such as CAD, hypertension and CHF, which often represent the etiopathogenetic substrate (Aronow, 2002, Chatap et al., 2002). These diseases
CHF and cognitive impairment
CHF is a mounting health problem that affects up to 10% of people over the age of 65 and it is associated with frequent hospital admissions, reduced quality of life, significant morbidity, and increased mortality in the developed world; CHF patients have also a high readmission rates ranging from 40 to 50% within 6 months (Abete et al., 2013). Some readmissions may be the consequence of the presence of cognitive impairment which is particularly common in CHF patients ranging from 30% to 80% (
CVD, self-care and cognitive impairment
Self-care maintenance in CVD patients represents a critical point of the treatment adherence including reducing risk factors, following dietary restrictions, taking multiple medications, performing daily weights, exercising to prevent deconditioning, and having a good social support (Mazzella et al., 2010, Harkness et al., 2014). However, cognitive impairment may represent a serious obstacle in the management of the patient with cognitive decline. It has been demonstrated in 60 hypertensive
CVD, mortality and cognitive impairment
Controversial data is available on the association between mortality, CVD and cognitive impairment in the elderly. In a cross-sectional survey with a 6-year mortality evaluation conducted in a region of southern Italy, involving elderly subjects with and without cognitive impairment. Mortality shows a linear relationship with pulse blood pressure and a U-curve shape for diastolic blood pressure. This phenomenon was more evident in subjects with cognitive impairment showing the greatest risk of
The heart–brain continuum hypothesis
Advances in pathophysiological research suggest that the cardiovascular disease continuum begins with risk factors (hypertension, dyslipidemia, obesity, diabetes, smoking, etc.) that initiate the process that leads to tissue damage (Dzau et al., 2006). In this context, the role of hypertension through all stages of cardiovascular disease has been clearly illustrated by a prospective longitudinal analysis of 36-year follow-up data from the Framingham Heart Study. This analysis showed that the
Conclusions
The analysis of the data allows concluding that:
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CVD affect the development of cognitive impairment in the elderly;
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some discrepancies are mainly related to selection bias of the study populations;
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hypertension, CAD, atrial fibrillation and CHF and appear to be connected by a cardiovascular continuum;
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thrombo-embolic and/or reduction of cardiac output appear to be the main mechanisms in the determination of cognitive impairment in the elderly with cardiovascular disease;
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CVD patients have great
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