Vol 9, No 1- Neuropsychiatry and Cardiovascular Disease
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ementia is one of the major causes of loss of autonomy,and the main reason for the institutionaliza- tion of the elderly.Epidemiological studies conducted in the last 10 years have shown that the prevalence of dementia is close to 5% in the population over 65 years of age.These studies have also shown that its prevalence increases sharply with age,and as a result of the expected shift in population demographics,the incidence and prevalence of dementia are expected to increase dramatically over the coming decades.The number of demented patients worldwide is projected to increase from 24.3 million in 2001 to 81.1 million in 2040.1 Significantly,the vast majority of new cases are expected to appear in developing countries.For example,the num- ber of demented persons in China and India will increase by 300% during this period.1Prevention and management of dementia are therefore a major public health challenge in the majority of countries around the world. As a general rule,the occurrence of dementia is not a sudden phenomenon.It is the final stage of cognitive deterioration,the speed of which varies from one indi- vidual to the other.However,even in cases where its development is rapid,the process is measured in terms of months.Taking into account the life expectancy of indi- viduals at risk,retarding the development of dementia for a few months may have important consequences on the prevalence of dementia.2 Such expectations have been raised in recent years with the discovery of a relationship between hypertension and dementia.Overall,published studies suggest that high blood pressure increases the risk of cognitive decline and dementia,and therefore,that lowering blood pressure might reduce this risk.This paper will review the evi- dence for this,and will discuss some of the important questions that remain unanswered. C l i n i c a l  r e s e a r c h D Copyright © 2007 LLS SAS. All rights reserved www.dialogues-cns.org Hypertension,cognitive decline,and dementia:an epidemiological perspective Christophe Tzourio,MD,PhD Keywords:hypertension; elderly; stroke; cognition; dementia; Alzheimer's disease; white matter lesion; magnetic resonance imaging; trial Author affiliations: INSERM U708 Neuroepidemiology, Paris, France; Department of Neurology, Hôpital Lariboisière, Paris, France Address for correspondence:Dr Christophe Tzourio, INSERM U708, Hôpital de la Salpêtrière, 75651 Paris Cedex 13, France (e-mail: tzourio@chups.jussieu.fr) Hypertension is a known risk factor for stroke, and thus for vascular dementia. However, recent large observa- tional studies have suggested that high blood pressure may also play a role in Alzheimer’s disease. The mech- anisms linking hypertension to Alzheimer’s disease remain to be elucidated, but white matter lesions seen on cerebral magnetic resonance imaging appear to be a good marker of this association. It is not yet clearly established whether lowering blood pressure reduces the risk of white matter lesions and dementia, so large trials dealing with this question are eagerly awaited. These future trials could confirm the hope that, by low- ering blood pressure, we may have a preventive treat- ment for dementia. This issue is of major importance, as the number of cases of dementia is expected to rise sharply in the near future. © 2007, LLS SAS Dialogues Clin Neurosci. 2007;9:61-70.