Unravelling the Genetics of Early and Late-onset Alzheimer’s

Down's Syndrome, a potential model for the pathogenesis of Alzheimer's disease

Nariman Malik, BSc

Alzheimer's disease (AD) is the most common cause of dementia in the elderly.1 It affects more than 5% of all people age 65 and over and about 25% of those aged 85 and over.2,3 This devastating disease is characterized by a progressive loss of cognitive abilities, usually beginning with short-term memory difficulties and progressing to include language, visuospatial and executive dysfunction.1 Mean survival time following a diagnosis of Alzheimer's disease is about 8 years and death usually occurs as a result of intercurrent disease.4 In 1991, the Canadian Study of Health and Aging estimated that over 160,000 Canadians met the criteria for Alzheimer's disease.5 If the current trends continue, by the year 2031 the number of cases are predicted to triple while the population will have only increased by a factor of 1.4.5

The main risk factors for developing AD are advancing age and family history. The disorder can be classified as familial or sporadic. Familial cases are usually early-onset (onset before age 65), while sporadic cases are usually late-onset (onset after 65). The majority of cases of AD are sporadic. Individuals with a first degree relative with sporadic AD, are at twice higher risk of developing the condition.