Finally, dementia almost always is thought to be a concern for people further along in age, but that is not true across the board. Not only do things we do in our earlier years often play a role in the development of dementia, but people as young as 30 have been diagnosed with the condition. In a 2017 study published in the European Journal of Neurology, researchers found that between 38 and 260 people per 100 000 individuals experience the onset of dementia between 30 and 64 years of age. And 420 per 100,000 people develop the disease between the ages of 55 and 64. And for more helpful information on health, entertainment, and more delivered straight to your inbox, sign up for our daily newsletter.