American biohacker Bryan Johnson invests big money – an estimated US$2 million yearly – trying to turn back his body clock. His quest for eternal youth includes specialised nutrition, supplements and personalised medicine – from stem-cell injections to DNA editing.
Chronological vs biological age
The number of years you have lived represents an “incomplete account of the ageing process”, says Professor Cathal McCrory, a co-principal investigator of The Irish Longitudinal Study on Ageing, or Tilda, at Trinity College Dublin in Ireland.
“Consider two same-aged peers of 50. The number of years that have passed is technically the same for both of them, but the ageing experience may be very different. Even identical twins age differently, despite sharing 100 per cent of their DNA,” he says.
British journalist and author Sandra Parsons exemplifies how to slow ageing. She has engineered her “real” age – 63 – down by 40 years or so.