Early on-set Alzheimer's is usually caused by a genetic mutation which runs in families. There are less than 500 known families in the world with one of the three known genetic mutations which lead to the disease. However, there appears to be a bit of a growing number of individuals being diagnosed with early on-set Alzheimer's.
This raises a number of questions. Is better diagnostics leading to more individuals having their symptoms recognized earlier? Is it actually early on-set Alzheimer's or another form of dementia such as Lewy Body Dementia? Are there more causes to early on-set Alzheimer's than just these three mutations?
It is too early to say and the trends will have to be watched and patients will have to be tested to see if they actually have Alzheimer's and if there are more causes to it.