A variation of a much-studied gene involved in transmission of dopamine, a key component of the brain's reward-and-learning system, was found to be far more frequent among the very old, News.com.au reported.
Professor Robert Moyzis of the University of California, Irvine, said that the variant might not extend lifespan directly.
Instead, it appears to predispose those who bear it to a more vigorous lifestyle.
The human subjects in the study came from Laguna Woods, part of a group involved in the Leisure World Cohort Study that began in 1981. It included people who were 90 or older in 2003.
Most have since passed away, Prof Moyzis said.
But their genes, as well as cell lines, live on, perpetuated in laboratories so they will be available for research.
In this study, genetic samples from 310 people 90 years old or older were checked for the gene variant, known as the DRD4 7R allele.
Sixty-six percent more people possessed the variant in the 90-plus group when compared with a control group of nearly 3000, aged seven to 45.
The discovery of the gene variant's association with longevity might inspire people to become more active as they age, potentially extending their lives - even if they don't harbor the variant themselves, Prof Moyzis said.