Why some 80 year olds have memories like 50 year olds

People over the age of 80 who retain memory and thinking at the level of significantly younger people have, on average, at least two notable genetic advantages associated with Alzheimer's disease risk.

This was reported by a team at Vanderbilt University Medical Centre (VUMC); the findings are published in the journal Alzheimer's & Dementia.

The researchers studied variants of the APOE gene. The APOE-ε4 allele is considered the main common genetic risk factor for late-onset Alzheimer's disease, while APOE-ε2 is associated with a lower risk.

The analysis included data from 18,080 participants from eight national aging cohorts combined in the Alzheimer's Disease Sequencing Project Phenotype Harmonisation Consortium (ADSP-PHC). "Super agers" (super agers) were defined as people 80+ whose memory was above the average level shown by cognitively healthy participants 50-64 years old.

The first key difference was the rarer occurrence of APOE-ε4. Super-agers were 68 per cent less likely to be carriers of APOE-ε4 compared with people of the same age (80+) with dementia with Alzheimer's disease. But the most telling result, the authors say, is different: super-agers were 19% less likely to be APOE-ε4 carriers, even compared with cognitively healthy 80+ peers in the control group.

The second difference was an increased proportion of "desirable" APOE-ε2. Superagers were 28% more likely to be APOE-ε2 carriers than cognitively healthy 80+ controls, and 103% more likely than 80+ participants with Alzheimer's-type dementia.

The authors emphasise that the work is observational: it shows statistical relationships rather than a 'guarantee' of protection. However, according to the team, the super-age phenotype may become a useful tool for finding mechanisms of resistance to Alzheimer's disease and the reasons why some people retain a clear mind at a very old age.