Research

Dementia has a profound impact on patients, families,caregivers and society in general. Data from theCanadian Study of Health and Aging (CSHA) show that 252 600 people had dementia in Canada in 1991; proba-ble Alzheimer’s disease (AD) was diagnosed in 64 % of those people.1 It was also estimated that the net annual cost to soci-ety of care for dementia in Canada in 1991 was over $3.9 bil-lion.2 The prevalence of AD rises exponentially, doubling ap-proximately every 5 years between the ages of 65 and 85. In recent years, rapid progress in molecular genetics has fostered the discovery of at least 4 genes associated with AD: the amyloid precursor protein (APP), the presenilin-1 gene (PS-1), the presenilin-2 gene (PS-2) and the apolipoprotein E gene (ApoE).3–5 Mutations in APP, PS-1 and PS-2 account for virtually all autosomal dominant inherited early-onset forms of AD. However, this form of AD represents less than 10 % of all AD cases. By contrast, ApoE ε4 polymorphis