Scientists have devised a biological clock using DNA and hope to use it to slow ageing and fight cancer.
The clock compares the biological “age” of body tissue to a person’s age in years.
The clock was found embedded in genomes, which is the complete genetic make up of a person, and could help scientists discover why humans age and how to slow the process.
It was discovered that healthy female breast tissue was two to three years older than other tissue in the body.
However tissue next to tumours was 12 years older and the tumour tissue itself was 36 years older.
This could explain why breast cancer is the most common cancer in women and why age is a major risk factor for many cancers in both genders.
Results showed while most people’s biological age matched their true age, others differed significantly.
Professor Steve Horvath, of UCLA in Los Angeles, said: “To fight ageing, we first need an objective way of measuring it.”