ABSTRACT
References 534
The growing recognition of the role of vascular factors in Alzheimer’s disease (AD) challenges traditional dementia subclassification. In particular, the assumption that AD and vascular dementia (VaD) are distinguishable clinical disorders in late-onset dementia has become untenable because of the large pathological overlap and poor correlations between diagnosis and pathology. The problems this distinction has caused for research are now well recognized. The system of subclassifying dementia according to presumed AD or vascular aetiology emerged in the 1960s when dementia was occurring earlier in life, when treatment of vascular risk factors was limited and florid cerebrovascular disease was frequently present at post-mortem – i.e. could be assumed to be a single underlying cause. Dementia cases today, particularly in high income nations, are much more frequently arising in later old age (e.g. ninth and tenth decades) where mixed pathology is the norm. Developments in neuroimaging have been a mixed blessing: the ability to detect more minor levels of vascular disturbance is undoubtedly useful in investigating causal pathways; however, detectable ‘abnormalities’ are now frequently coincidental rather than causal, particularly in older age groups.
