People who carry a genotype that predisposes to Alzheimer's disease have a tendency to forget to do things, even if they don't have dementia.

Carrying a gene variant called Apo E4 is already known to increase the risk of Alzheimer's disease. Now a team at the University of New Mexico reveals how the variant has some subtle effects even in healthy individuals.

The researchers looked at a group of 32 people aged between 60 and 87 who were free from dementia. They were divided as to whether they did or did not carry the Apo E4 gene variant. Then they were given a test of prospective memory which involved remembering to write down a specific word when they were exposed to a target word. Prospective memory is important in everyday life - it's all about remembering to do things.

Those in the Apo E4 group were significantly worse at the prospective memory task than those who did not have Apo E4. Other studies have suggested that Apo E4 is linked with problems in episodic memory - remembering the past - as well. It's not clear if those in the Apo E4 group were, perhaps, in the very early stages of dementia and whether the prospective memory issue could be used as a diagnostic test. Even if dementia is not involved, people with Apo E4 could learn techniques that improve prospective memory.

Source
Neuropsychology January 2005