How Much Did Weekly Exercise Cut Alzheimer's Risk?

Going from completely sedentary to 15 metabolic equivalent hours a week produces probably a 50 percent reduction in risk, equal to half the benefit of going all the way. On Huberman Lab, nothing told to patients matters more for Alzheimer's prevention than exercise, and the small recommendations usually offered are not enough for the maximum benefit.

A metabolic equivalent is the energy of quiet sitting, about one metabolic equivalent. Sitting and talking uses about 1.3. Walking really briskly uses about five, so 15 metabolic equivalent hours a week is three one-hour brisk walks. The largest share of benefit comes from going from nothing to something, and that first step is what brings the 50 percent reduction. Personal skepticism on Huberman Lab puts the true reduction a bit under 50 percent, while the studies miss further upside. Exercising past 15 metabolic equivalent hours still adds benefit, though each added hour accrues more slowly.

Health span sits outside the risk numbers. It is the functional question of the marginal decade: picking up a great grandkid who comes running, getting up off the floor, and playing on the floor with a kid before standing up alone.