A chemical "fingerprint" in the blood may provide clues to an infant's health and rate of ageing near the end of life, research has suggested.
The discovery raises the prospect of a simple test at birth that could help doctors stave off the ravages of disease in old age.
Scientists identified 22 metabolites, small molecules linked to metabolism, that may be useful indicators of how we can expect to grow old.
One in particular, linked to a range of traits including lung function, bone density , blood pressure and cholesterol levels, was singled out by the researchers. It is also strongly associated with birthweight - itself a known determinant of healthy ageing.
Levels of this metabolite, C-glyTrp, could reflect accelerated ageing in later adulthood, the scientists believe. Higher levels of the molecule were associated with lower weight at birth in comparisons between pairs of identical twins.
Since identical twins share the same genes, this suggests that levels of the metabolite are altered by nutrition or different conditions in the womb.
Study leader Professor Tim Spector, from King's College London, said: "Scientists have known for a long time that a person's weight at the time of birth is an important determinant of health in middle and old age, and that people with low birthweight are more susceptible to age related diseases. So far the molecular mechanisms that link low birthweight to health or disease in old age had remained elusive, but this discovery has revealed one of the molecular pathways involved."
Prof Spector's team analysed blood samples donated by more than 6,000 twins. The researchers identified 22 metabolites directly linked to chronological age, with higher concentrations in older than in younger people.
Further work showed that the gene influencing levels of C-glyTrp could be modified by epigenetics, a process whereby environmental factors switch genes on or off and alter their activity.
The epigenetic changes may influence metabolism during a person's lifetime, thereby affecting susceptibility to age-related diseases. The findings are published in the International Journal of Epidemiology.