My 23andMe report says I have 'reduced risk' for Alzheimer's. Should I trust that?
Quick reality check on what 23andMe is actually telling you.
The Alzheimer's report from 23andMe checks two specific variants of the APOE gene - specifically, whether you carry the e4 allele, which is the best-established genetic risk factor for late-onset Alzheimer's. A "reduced risk" result means you carry zero copies of e4.
That is genuinely good news - APOE-e4 carriers have meaningfully elevated risk. But "reduced risk" relative to the average is not "no risk." Alzheimer's is influenced by many variants, almost all of which the consumer test does not look at, plus a substantial environmental component. The lifetime risk for someone with no APOE-e4 is still around 9–10% (versus 12–15% population average and 30–50% for one e4 copy and significantly higher for two).
So: the report is correct as far as it goes. It is just looking at one variant out of dozens that matter, on a condition where lifestyle and cardiovascular health are major contributors.
What to actually do with this information: nothing dramatic. The general advice for reducing Alzheimer's risk - control blood pressure, manage cardiovascular health, stay socially and cognitively active, exercise regularly, manage hearing loss if it develops - applies to you the same as to everyone else, regardless of what APOE says.
Adding from a clinical angle: the bigger problem with Alzheimer's APOE testing is on the other side. People who do get the "elevated risk" result sometimes spiral into anxiety about a condition they may not develop and cannot currently prevent in any specific way. This is one of the reasons many genetic counsellors advise people to think carefully before ordering DNA reports that include neurodegenerative conditions. The information is real, but the actionability is limited.
If you've already received a "reduced risk" result and you feel reassured, great. If a friend gets the opposite result and feels worse, that is also a foreseeable outcome of these tests.