New York: Genes appear to play a stronger role in people living up to extreme old age, according to a new study of siblings.
The study, published online in the Journal of Gerontology: Biological Sciences, found that for people who live up to 90 years of age, the chance of their siblings also reaching age 90 is about 1.7 times greater than for the average person born around the same time.
But for people who survive up to age 95, the chance of a sibling living to the same age is 3.5 times greater.
And for those who live up to 100, the chance of a sibling reaching the same age grows to about nine times greater.
At 105 years old, the chance that a sibling will attain the same age is 35 times greater than for people born around the same time -- although the authors note that such extreme longevity among siblings is very rare.
These much higher relative chances of survival likely reflect different and more potent genetic contributions to the rarity of survival being studied.
"They strongly suggest that survival to age 90 and survival to age 105 are dramatically different phenotypes or conditions, with very different underlying genetic influences," said lead researcher Paola Sebastiani from the Boston University.
The study analysed survival data of families of 1,500 participants in the New England Centenarian Study, the largest study of centenarians and their family members in the world.
Among those families, the research team looked at more than 1,900 sibling relationships that contained at least one person reaching the age of 90.
Sebastiani and co-author Thomas Perls said the findings advance the idea that genes play "a stronger and stronger role in living to these more and more extreme ages", and that the combinations of longevity-enabling genes that help people survive up to 95 years are likely different from those that help people reach the age of 105.