Scientists can now almost accurately predict a person's lifespan.

A team of researchers from the University of Edinburgh have identified a biological clock that provides vital clues about how long a person is likely to live.

Researchers studied chemical changes to DNA that take place over a lifetime, and can help them predict an individual's age. By comparing individuals' actual ages with their predicted biological clock age, scientists saw a pattern emerging.

People whose biological age was greater than their true age were more likely to die sooner than those whose biological and actual ages were the same.

Four independent studies tracked the lives of almost 5,000 older people for up to 14 years. Each person's biological age

was measured from a blood sample at the outset, and participants were followed up throughout the study.

Researchers found that the link between having a faster-running biological clock and early death held true even after accounting for other factors such as smoking, diabetes and cardiovascular disease.

Scientists from the University of Edinburgh, in collaboration with researchers in Australia and the US, measured each person's biological age by studying a chemical modi-fication to DNA, known as methylation. The modification does not alter the DNA sequence, but plays an important role in biological processes and can influence how genes are turned off and on. Methylation changes can affect many genes and occur throughout a person's life.