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 M… - David A. Sinclair

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.

Over fifty years, Goldman estimated, the potential economic benefits of delayed aging would add up to more than $7 trillion in the United States alone. And that's a conservative estimate, based on modest improvements in the percentages of older people living without a disease or disability. Whatever the dollar figure, though, the benefits "would accrue rapidly," Goldman's team wrote, "and would extend to all future generations,"

We can't prevent all DNA damage — and we wouldn't want to because it's essential for the function of the immune system and even for consolidating our memories57 — but we do want to prevent extra damage. And there's a lot of extra damage to be had out there. Cigarettes, for starters. There aren't many legal vices out there that are worse for your epigenome than the deadly concoction of thousands of chemicals smokers put into their bodies every day. There's a reason why smokers seem to age faster: they do age faster. The DNA damage that results from smoking keeps the DNA repair crews working overtime, and likely the result is the epigenetic instability that causes aging. And although I'm not likely to be the first person you'll hear this from, it nonetheless bears repeating: smoking is not a private, victimless activity. The levels of DNA-damaging aromatic amines in cigarette smoke are about fifty to sixty times as high in secondhand as in firsthand smoke.58 If you do smoke, it is worth trying to quit.