Traditionally a person’s age has been measured by the number of years alive. However, this measure has recently come into question; we have discovered genes that slow ageing in centenarians, leading to healthier old age in some people.⁵

Different tissues in the same body can age at vastly different rates as well, which may depend on genetic or environmental factors⁶. To create better measures of age, new strategies are investigating age-related variations in blood markers, DNA methylation states, or patterns of locomotor activity⁷,⁸ and these may explain differences in longevity. AI technologies are being developed to combine many such factors.⁹,¹⁰ These more precise measurement of age-related health can then more precisely evaluate the anti-ageing merits of competing preventive drugs, diets, supplements, and exercise regimes. It may also validate targeted ways of living to “minimise” your personal age, such as food clocking, ketogenic diets and fasting.