105 and still alive: Study finds rate of death decreases for world's oldest people

The oldest person in the world, as far as anyone knows, was a French woman who lived to be 122, according to the Guinness World Records. But a new study published today shows that age might just be a number -- and that a person's risk of death actually decreases after the age of 105.

Research conducted by the Italian National Institute of Statistics (ISTAT) and published in the journal Science Advances revealed this odd truth: someone who is 106 actually has a lower risk of death than someone who is 102.

To get their results, ISTAT researchers collected and validated a sample of 3,836 people older than 105 from 2009 to 2015. The majority of the people studied were women, and 463 were men. To ensure as much accuracy in ages as possible, the study verified subjects' ages using their birth certificate and confirmation of the data from a civil status officer.

Researchers found that after the age of 80, the death rates began decreasing, plateauing at 105. Of course, this does not mean that people over the age of 80 or over the age of 105 don't die. Instead, the results show that the death "rate" -- how many people die in a particular time period -- slows down.

For the researchers, this data implies that the upper limit of the human lifespan has not yet been reached and that people may live beyond Jeanne Louise Calment's world record of 122 years and 164 days.

Benjamin Gompertz, a British mathematician, put forth an 1825 proposal that introduced the concept of an "upper limit" to age. However, as time goes on, and scientific advances allow people to live longer, the mindset around aging has changed.

While 60 used to be considered "old," society now looks on people of that age as productive, not senescent.

This study's data suggests that longevity is fluid and continually increasing over time and that a limit has not yet been reached.

It is important to note that getting reliable, accurate ages for the oldest people in the world can be difficult in populations where recording data was not efficient a century ago. Furthermore, even if recording data is efficient, there may be a tendency to exaggerate extreme age.

Using data from a single nation with a clear study design, as these researchers did, means that their findings could be repeated by others, resulting in more answers to the question of how long people can live. But the study did have its limits: because it only looked at Italians, the results might not be generalizable to other populations.

As for Calment, the woman who died at the age of 122 in 1997, she filled her long life with exercise and almost two pounds of chocolate per week, according to Guinness World Records.

She also maintained her sense of humor. When asked at her 120th birthday celebration what kind of future she expected, she replied: "A very short one."

Denise Powell, M.D. candidate, is a student from Jackson, Mississippi, working in the ABC News Medical Unit.