DNA accumulates mutations. The protective ends of chromosomes erode away. Mitochondria, the cell’s energy factory, falter and break down. The immune system goes haywire. The reserve pool of stem cells dwindles, while some mature cells enter a zombie-like state, spewing toxic chemicals into their environment. The picture sounds dire, but it’s not all bad news. ...

People are living longer than ever, but there’s growing recognition that longer life expectancy is of little use unless we also delay the physical decline associated with old age. New research suggests doing so could be worth trillions of dollars in economic gains. Over the last century, life expectancy has shot up across the world thanks to improvements in ...