ReviewVascular cognitive impairment in dementia
Introduction
Ageing populations face an increase in disease burden from chronic neurodegenerative conditions. Dementia will be a major contributor to this increased burden [1]. Cerebrovascular disease is thought to be the second most common cause of dementia and a spectrum of cognitive disorders related to cerebrovascular disease is now recognised [2]. Accordingly, the cognitive impairment associated with brain vascular disease is an increasingly important and recognised area of the medicine of older people. Despite the critical importance of dementia, there is still inconsistent definition of the major sub-types. There is increasing recognition that many, if not most, older people with dementia have mixed, or overlapping, disease due to both vascular and Alzheimer's type changes. However the concept of “mixed dementia” remains variably recognised and operationalised. In this context, the nature, importance and management of vascular cognitive impairment are reviewed.
Section snippets
Methods
This narrative review provides a brief overview of traditional teaching, and more recent research findings, relevant to clinical practitioners in the field ordered using a clinical approach. In addition, the “state of the art” was specifically considered in a search of the Medline indexed English language human studies published in the last 12 months (to April 2014) using the search terms “dementia” or “Alzheimer disease”, and “cerebrovascular disorders” or “stroke” or “cerebral infarction” or
Clinical definitions
Traditional teaching described vascular (or “multi-infarct”) dementia as the second leading type of dementia, usually with relatively abrupt onset and stepwise decline, related to multiple large volume or lacunar brain infarcts. Also included were people who may have had fewer strokes, but the strategic position of the lesions(s) and temporal relationship to the onset of cognitive impairment suggested aetiological relevance. Increasingly a broader spectrum of cognitive disorders associated with
Aetiology and convergence of risk factors for the major dementias
Age and the major traditional vascular risk factors (hypertension, smoking, diabetes and hypercholesterolemia) account for the majority of a person's lifetime risk of cardiovascular events [10]. The presence of vascular risk factors such as hypertension and diabetes in midlife is negatively associated with subsequent cognitive function in older age [11], [12]. In addition to predicting atherosclerotic disease, these “vascular” risk factors also predict, and appear to promote development of,
Epidemiology
Given that dementia and vascular disease are strongly age related, population ageing will be associated with absolute increases in the overall burden of dementia and stroke. Stroke and dementia frequently co-exist; around one in ten patients have dementia prior to their first stroke, increasing to one in five within the first year after first stroke, and over one in three within the first year after recurrent stroke [21]. Relatively, chronic neurodegenerative conditions (of which dementia is
Anatomic and functional correlates
Traditional teaching emphasised the distinct pathological processes of vascular disease and neurodegeneration secondary to Alzheimer's pathology. These distinctions now appear to be less relevant clinically, given that people surviving to old age frequently have co-existent changes of both Alzheimer's type pathology and vascular disease [24]. Healthy adults have substantial cerebral reserve and thus many older people have sub-clinical disease. For example, it is not uncommon for an older person
Clinical correlates and differential diagnosis
Structural vascular brain disease is thought to cause cognitive impairment through strategic cortical infarcts, infarction of the basal ganglia or thalamus, or disruption of white matter tracts by lacunar infarcts or small vessel disease. Strategic infarcts will cause a pattern of cognitive deficits according to the infarct location [34]. Subcortical vascular cognitive impairment is characterised by relative preservation of memory with impaired cognitive speed, attention and executive function
Prevention
Given the challenge of reversing established brain vascular disease, prevention is a cornerstone of management. Lifestyle interventions, including physical and cognitive activity are often recommended to maintain wellbeing in middle and later life. There is evidence that physical activity has beneficial effects on endothelial function [32] and may prevent cognitive impairment [38]. Improved control of vascular risk factors in mid-life is assumed to be a key strategy to reduce the burden of
Treatment of vascular cognitive impairment in dementia
Although traditional teaching was that nervous system lesions were essentially irreversible, the potential for plasticity of the nervous system is increasingly recognised. Neuroplasticity persists in ageing brains, and facilitates recovery from acute stroke lesions [42]. The potential for plastic remodelling in the face of neurodegeneration or chronic small vessel disease is less well understood. Systematic review of the randomised studies of cognitive rehabilitation or cognitive training in
What is the current state of the art?
The search produced 29 clinical trials of which 22 were excluded because of limited relevance. Additionally, one letter and one protocol paper were excluded (see supplementary material). Included studies are summarised in Table 1. The included studies are all observational [49], [50], [51], [52], [53]. They highlight that, despite twenty years of literature regarding the relationship between cerebrovascular and Alzheimer's disease, current work continues to try to unravel the associations
Conclusion
In the context of increasing longevity, clinicians can expect to care for increased numbers of older people living with cognitive impairment. Given the intertwined risk factors for the major causes of cognitive impairment, prevention by control of vascular risk factors, and addressing lifestyle factors is important. A spectrum of cognitive disorders related to brain vascular disease is recognised and careful clinical assessment is required to understand the significance of the various
Contributors
C.E.B. designed the review, extracted the references, drafted and critically revised the manuscript.
Competing interests
None.
Funding
The author has received no funding for this article.
Provenance and peer review
Commissioned and externally peer reviewed.
Acknowledgements
Swithin Song's assistance providing Fig. 1, Fig. 2 is gratefully acknowledged. Frederik Barkhof's permission to reproduce Fig. 3 (originally published at http://www.radiologyassistant.nl/en/p43dbf6d16f98d/dementia-role-of-mri.html) is gratefully acknowledged.
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