Tech entrepreneur Bryan Johnson is spending millions a year trying to reduce his biological age - how old his body seems, rather than his actual chronological age, which is 45.
There's a good reason for any of us to do this. Age is the highest risk factor for disease, whether it's cancer, type 2 diabetes, heart disease, or dementia, so if ageing as a whole could be delayed, then so could the risk of onset of these conditions. For him though, it's a sport.