Alzheimer’s disease is practically unheard of in adults younger than 40, and very rare (one in 2,500) for those under 60. It affects 1 percent of 65-year-olds, 2 percent of 68-year-olds, 3 percent of 70-year-olds. After that, the odds start multiplying. The likelihood of your developing Alzheimer’s more or less doubles every five years past 65. Should you make it to 85, you will have, roughly, a fifty-fifty shot at remaining sane.
