FIRST-BORN children of young mothers have the best chance of living to 100, new research suggests.
Scientists in Chicago, USA, made the discovery after studying the family histories of 198 centenarians born between 1875 and 1899.
First-born children are 1.7 times more likely than their siblings to live to 100.
Having a young mother at the time of birth was an even stronger predictor of longevity.
People whose mothers were under 25 when they were born were twice as likely to survive beyond a century.
The researchers suspect the age of the mother is important.
First-born children are more likely to have younger mothers, who may have better quality eggs.
They may also be less likely to have infections that might cause long-term damage.