Ms. Morano has no doubts about how she made it this long: Her elixir for longevity consists of raw eggs, which she has been eating — three per day — since her teens when a doctor recommended them to counter anemia. Assuming she has been true to her word, Ms. Morano would have consumed around 100,000 eggs in her lifetime, give or take a thousand, cholesterol be damned.

She is also convinced that being single for most of her life, after an unhappy marriage that ended in 1938 following the death of an infant son, has kept her kicking. Separation was rare then, and divorce became legal in Italy only in 1970. She said she had plenty of suitors after that, but never chose another partner. “I didn’t want to be dominated by anyone,” she said.

Gerontologists agree that there is no one key to longevity. “You talk to 100 centenarians, you get 100 different stories,” said Valter D. Longo, the director of the Longevity Institute at the University of Southern California, whose studies suggest that diet is an important factor in living longer.

And there’s genetics. “We do know that the ability to make it to 110 is heritable, so you have a large increase in chance if you have several people in your family to live to a late age,” Dr. Longo said.

One of Ms. Morano’s sisters died just short of 100; another lived to 102.

Remarkably, Ms. Morano still lives alone, shuffling around a tiny two-room apartment surrounded by dusty memories and the vestiges of her more recent fame, including tributes and certificates from officials, among them the country’s last president, commending her resilience. Next to her bed is a small plaque with the numbers “115” in bright blue letters, made by children at a local nursery school, who hand-delivered the present.