Using your nondominant hand, write your name, address, and phone number while circling your opposite foot counterclockwise. - David A. Sinclair

But the true extent to which the survival circuit is conserved between yeast and humans wasn't fully known until 2017, when Eva Bober's team at the Max Planck Institute for Heart and Lung Research in Bad Nauheim, Germany, reported that sirtuins stabilize human rDNA.23 Then, in 2018, Katrin Chua at Stanford University found that, by stabilizing human rDNA, sirtuins prevent cellular senescence — essentially the same antiaging function as we had found for sirtuins in yeast twenty years earlier.24

Small numbers of senescent cells can cause widespread havoc. Even though they stop dividing, they continue to release tiny proteins called cytokines that cause inflammation and attract immune cells called macrophages that then attack the tissue. Being chronically inflamed is unhealthy: just ask someone with multiple sclerosis, inflammatory bowel disease, or psoriasis. All these diseases are associated with excess cytokine proteins.

And because aging isn't a disease by the commonly accepted definition, it doesn't fit nicely into the system we've built for funding medical research, drug development, and the reimbursement of medical costs by insurance companies. Words matter. Definitions matter.