On Sunday, Kane Tanaka celebrated her birthday with a party at a nursing home in Fukuoka, Japan. Dressed in a gold kimono with a cluster of purple flowers tucked behind her ear, she enjoyed a big birthday cake.

“Tasty,” she said after the first bite, as quoted by Reuters. “I want some more.”

Staff members, friends and a local broadcast crew were there to witness the occasion, which marked Tanaka’s 117th birthday. With the passing of this staggering milestone, Tanaka remains the oldest person in the world—a title she formally claimed last year, when Guinness World Records confirmed her supercentenarian status.

Tanaka was born on January 2, 1903. The seventh out of eight children, she married Hideo Tanaka shortly after turning 19. The couple had four children and adopted a fifth. When her husband was called to join the military during the Second Sino-Japanese War in 1937, Tanaka took a leading role in the family business, which made and sold sticky rice, udon noodles, and zenzai, a traditional Japanese sweet.

Since turning 100, holding the record for the world’s oldest person has been Tanaka’s dream, according to Lateshia Beachum of the Washington Post. The moment she had been hoping for came in March of last year, when Guinness World Records presented her with official certificates during a ceremony at her nursing home. (“I don’t know what this is,” she said when the framed record was placed in her hands.) Tanaka was also treated to flowers and a box of chocolates, which she opened immediately, announcing her intention to eat 100 of the sweets.

A leading authority tracking supercentenarians, or people over 110 years old, is the Gerontology Research Group, which not only keeps a standardized database of the world’s oldest people, but also conducts interviews and biological research with the goal of developing drugs that will slow down the aging process, reported Rachel Nuwer for Smithsonian magazine in 2014. To make it onto the list, supercentenarian candidates must present at least two pieces of documentation proving their age, a current photo ID, and, for women who took their husband’s name after marriage, proof of the name change.

But monitoring the world’s most senior citizens is not a foolproof process. Fraud can come into play, as may have been the case with Jeanne Louise Calment, who died at the age of 122 in 1997 and is considered history’s oldest documented person. A recent study posited that Calment died at the age of 59, leaving her daughter, Yvonne, to assume her identity in an attempt to avoid paying inheritance taxes. Experts have since disputed this claim.

The quality of record-keeping may also influence the supercentenarian count. Japan, for instance, boasts the world’s oldest population, with more than 71,000 centenarians. Longevity among the country’s population has been attributed to factors like healthy culinary traditions, but as Nuwer points out, Japan has also been keeping meticulous birth records for more than a century.

“[I]ndividuals who don’t make the cut likely are genuine supercentenarians,” she writes of the Gerontology Research Group list, “but they are unable to provide the documentation to prove it.”

Even if there are more supercentenarians than experts can reliably confirm, making it to such an advanced age is an exceptional feat. Just one in 1,000 people who live to the age of 100 will see their 110th birthday, according to Vox’s Kelsey Piper.

There are about 150 verified supercentenarians in the world, but as Amy Harmon reports for the New York Times, amateur genealogists estimate that number may reach 1,000 when unverified individuals are taken into account. Regardless, the group still represents a very small demographic.

Genetics may play a role in helping a very select few live so long, but scientists have struggled to identify other unifying factors that drive extreme longevity.

“I’ve interviewed more supercentenarians than probably anyone else, trying to find out what they have in common,” the late L. Stephen Coles, co-founder of the Gerontology Research Group, told Nuwer in 2014. “The answer is almost nothing.”

As experts work to identify the secrets to exceptionally old age, Tanaka is happy to simply keep living life at her nursing home. She wakes up at 6 a.m. and spends her afternoon studying mathematics. She is a fan of the strategy board game Othello, often besting the home’s staff.

Last year, when Tanaka received her record for the world’s oldest person, she was asked about the happiest moment in her long life. Her reply was simple: “Now.”