Natural history of vascular dementia

Knowledge about the natural history of vascular dementia (VaD) provides one context for assessing efficacy in pharmacological drug trials. We reviewed the literature for original studies reporting either (a) duration of survival or (b) cognitive status following a diagnosis of multi-infarct dementia (MID). Among 13 papers (combined sample size = 470; mean duration of follow-up = 4.3 years), survival was significantly shorter following a clinical diagnosis of MID compared with Alzheimer disease (AD). Nine studies (combined sample size = 175; mean duration of follow-up = 2.9 years) reported at least two mental status scores separated by at least 1 year. Among four studies using the Mini-Mental State Examination, no consistent differences in annualized rate of decline could be observed for MID compared with AD. Also, no factors were identified that predict rate of decline. This review reveals many limitations in our current knowledge about the natural history of VaD. Understanding would be enhanced by multinational harmonization of definitions for study entry point, diagnosis of VaD, classification of subtypes, as well as cognitive, functional, and behavioral endpoints.