Inherited Alzheimer’s Detectable 20 Years Before Symptoms Emerge

Identifying Alzheimer's Disease (AD) in its earliest stages is a top priority for researchers. Many scientists suspect that by the time symptoms become apparent, Alzheimer's disease has already damaged the brain extensively, making it difficult or impossible to restore memory and other mental abilities. Randall Bateman, from Washington University School of Medicine (Missouri, USA), and colleagues involved in Dominantly Inherited Alzheimer's Network (DIAN), an international study of inherited forms of AD, report that inherited forms of Alzheimer's may be detectable as many as 20 years before problems with memory and thinking develop.  Initial DIAN results confirm and expand upon earlier insights from studies of the more common sporadic forms of Alzheimer's, including data suggesting that changes in the levels of biological markers in the spinal fluid can be detected years before dementia. DIAN researchers are studying members of families who have mutations in one of three genes: amyloid precursor protein, presenilin 1 or presenilin 2. Participants with these mutations are certain to develop Alzheimer's disease early, with symptoms beginning in their 50s, 40s, or, in some rare cases, 30s. With 184 participants enrolled, the data produced has enabled initial comparisons among participants who carry a genetic mutation for Alzheimer's but are still asymptomatic, those who have a mutation and have Alzheimer symptoms, and those who do not have a mutation and thus are unaffected. By looking at the age of symptom onset in a parent who passed an Alzheimer's mutation to a DIAN participant, scientists can establish an estimated age of onset for a study participant. If a parent developed dementia at the age of 50, they would expect a child who inherited the mutation to develop dementia at roughly the same age. As a result, scientists can start amassing a detailed chronology of disease progression that covers the many years Alzheimer's is active in the brain but still before the onset of dementia.