Analysis of data from 418 older adults (70+) has found that carriers of the ‘Alzheimer’s gene’, APOEe4, were 58% more likely to develop mild cognitive impairment compared to non-carriers. However, ε4 carriers with MCI developed Alzheimer’s at the same rate as non-carriers. The finding turns prevailing thinking on its head: rather than the gene increasing the risk of developing Alzheimer’s, it appears that it increases the risk of MCI — and people with MCI are the main source of new Alzheimer’s diagnoses.
In this regard, it’s worth noting that the cognitive effects of this gene variant have been demonstrated in adults as young as the mid-20s.
The finding points to the benefit of genetic testing for assessing your likelihood of cognitive impairment rather than dementia — and using this knowledge to build habits that fight cognitive impairment.
 . The apolipoprotein E genotype predicts longitudinal transitions to mild cognitive impairment but not to Alzheimer's dementia: Findings from a nationally representative study. Neuropsychology. 2013 ;27(1):86 - 94.