Frenchwoman Jeanne Louise Calment was 122 years and 164 days old when she died in 1997. U.S. researchers said Wednesday that it is highly unlikely that Calment will lose the title of the oldest person in the world to anyone anytime soon.

A study published Wednesday in the journal Nature found that the human life span has reached its maximum limit — close to 115 years of age.

Improvements in areas such as public health, diet and environment have led to a continuous rise of average life expectancy since the 19th century. Since the 1970s, the human life span has also steadily increased. But researchers from Albert Einstein College of Medicine in New York found that this steady increase has hit the ceiling.

“Demographers as well as biologists have contended there is no reason to think that the ongoing increase in maximum lifespan will end soon,” senior author Jan Vijg said in a statement. “But our data strongly suggest that it has already been attained and that this happened in the 1990s.”

Researchers analyzed data from the Human Mortality Database and the International Database on Longevity. The Human Mortality Database compiles mortality and population data from over 40 countries. Using this data, researchers determined that the countries in the database still show a steady increase in average life expectancy rate at birth over the last century.

The number of people over 70 years of age has increased since 1990 but their survival rates compared to those over 100 years of age differ greatly. Researchers found that people over 70 show gains in terms of survival improvements. These gains peaked at 100 and then declined rapidly.

“This finding indicates diminishing gains in reducing late-life mortality and a possible limit to human lifespan,” Vijg said.

When analyzing data from the International Database on Longevity, the researchers focused on the maximum reported age of death and on people who were 110 or older between 1968 and 2006 in four countries — the United States, France, Japan and the United Kingdom. These countries reported the largest number of people who’ve lived the longest. The maximum reported age of death for people aged 110 or older, called supercentenarians, increased rapidly from 1970 until the early 1990s by about 0.15 years every year. But between 1995 and 1997, the maximum reported age of death reached a plateau.

Using this data, the researchers concluded that the average maximum human life span would be 115 years with the absolute limit being 125 years. However, the researchers added that the likelihood of a person living up to be 125 years old anywhere in the world is less than one in 10,000.

“While it’s conceivable that therapeutic breakthroughs might extend human longevity beyond the limits we’ve calculated, such advances would need to overwhelm the many genetic variants that appear to collectively determine the human lifespan. Perhaps resources now being spent to increase lifespan should instead go to lengthening healthspan—the duration of old age spent in good health,” Vijg added.