Some say 115 is lifespan limit, others disagree
McGill biologists say they believe there is no detectable limit to how long humans can live
Jeanne Calment liked cream cakes, a nightly glass of port and, when she was 110, acquired a taste for those strong, dark and lethally chic French cigarettes, Gauloises.
Calment, the oldest documented person who ever lived, died in 1997 at age 122.
So last October, when Albert Einstein College of Medicine researchers concluded Calment was a statistical outlier, and that the biological limit to the human lifespan is peaking at around 115, the proclamation, published in the journal Nature, made headlines worldwide.
“From now on, this is it. Humans will never get older than 115,” Jan Vijg, an Einstein expert on aging, told The New York Times.
Now, however, two Canadian biologists, in a critical comment published in Nature, argue the Einstein supercentenarian analysis was flawed and that there’s no evidence the maximum human lifespan has reached a plateau.
“We just don’t know what the age limit might be,” McGill experimental biologist Siegfried Hekimi said in a statement. “In fact, by extending trend lines, we can show that maximum and average lifespans could continue to increase far into the foreseeable future.”
Hekimi, a 60-year-old professor of biology and former professional cyclist (his most memorable race was the Tour de France in 1982), works with worms and mice. His lab has shown that by making a single change in the smallest piece of DNA of nematode worms, the animals can live five times longer, work that could one day open the door to interventions to slow our own biological rate of aging.
Hekimi believes it’s not out of the realm of possibility that humans could live to 150, or beyond. Longer life, he adds, doesn’t necessarily mean extra years of poor health. Observational studies of centenarians show that people aren’t “hanging in, staying alive, despite disease,” he said in an interview. “They just didn’t get sick.
“Whether it was luck or their genotype, that can be a debate. But the fact is that mostly the people who live a very long time, they were always healthy. They didn’t have heart disease or diabetes.”
Almost unavoidably, he said, an increased lifespan means a longer, healthy lifespan. (Though virtually blind and hard of hearing, and apart from mild heart failure and rheumatism, Jeanne Calment had reportedly been in good health a month before she died.)
When the Einstein study was published in October, putting the biological limit to human life at 115 years, “it was obvious to me this was a weak analysis,” Hekimi said.
“Further progress against infectious and chronic disease may continue boosting average life expectancy,” Vijg said when the study was released, “but not maximum lifespan.” But when they analyzed the same data, Hekimi and co-author Bryan Hughes questioned why the Einstein team split the data into two groups: one before a certain arbitrary date and one after.
Without dividing the data set in two, the McGill duo found a longterm increasing trend in maximum life, with no current evidence of plateauing. Theirs is one of five critiques of the original paper.
Since Confederation in 1867, Canadians’ life expectancy has more than doubled to 82 (80 for men, 84 for women). Hekimi says it stands to reason maximum lifespan will follow the same trend, meaning there’s no indication that while average lifespan goes up maximum lifespan won’t go up in parallel.
“If this trend continues and our life expectancy of the average person becomes 100, the longest person might make it to 150,” he said.
The oldest Canadian alive today is Ellen “Dolly” Gibb, of North Bay, Ont., who celebrated her 112th birthday in April.