Former first lady Barbara Bush died Tuesday at the age of 92, a family spokesman said.

Family spokesman Jim McGrath confirmed the death in a statement. The cause wasn't immediately known.

McGrath said Sunday that Bush, who was born in New York, was in "failing health'' and wouldn't seek additional medical treatment.

McGrath issued a news release Sunday saying that following a recent series of hospitalizations and after consulting with her family and doctors, the 92-year-old former first lady has decided not to seek additional medical treatment and will instead focus on comfort care. He did not elaborate as to the nature of Bush's health problems.

She had been in the hospital recently for congestive heart failure and chronic obstructive pulmonary disease. In 2009, she had heart valve replacement surgery and had a long history of treatment for Graves' disease, a thyroid condition.

"My dear mother has passed on at age 92. Laura, Barbara, Jenna, and I are sad, but our souls are settled because we know hers was," former President George W. Bush said in a statement Tuesday. "Barbara Bush was a fabulous First Lady and a woman unlike any other who brought levity, love, and literacy to millions. To us, she was so much more. Mom kept us on our toes and kept us laughing until the end. I'm a lucky man that Barbara Bush was my mother. Our family will miss her dearly, and we thank you all for your prayers and good wishes."

George H.W. Bush held his wife's hand all day Tuesday and was at her side when she died, according to Jean Becker, chief of staff at George H.W. Bush's office in Houston.

A funeral is planned Saturday at St. Martin's Episcopal Church in Houston, which Mrs. Bush and her husband regularly attended. Mrs. Bush will lie in repose Friday at the church for members of the public who want to pay respects. Saturday's service will be by invitation only.

"Barbara Bush challenged each of us to build a better world by empowering people through literacy. As only one of two women in American history who can be called First Lady and First Mother, she was matriarch of a family that remains as dedicated to public service as it was to politics," said former Secretary of State and White House Chief of Staff James Baker III.

The snowy-haired Mrs. Bush was one of only two first ladies who was also the mother of a president. The other was Abigail Adams, wife of John Adams and mother of John Quincy Adams.

Mrs. Bush's plainspoken manner and utter lack of pretense made her more popular at times than her husband. She brought a grandmotherly style to buttoned-down Washington, often appearing in her trademark fake pearl chokers and displaying no vanity about her white hair and wrinkles.

She married George H. W. Bush in 1945. They had six children and were married longer than any presidential couple in American history.

Barbara Bush's life

She was born June 8, 1925 in the city.

A distinct relative of President Franklin Pierce, Barbara Bush was raised in Westchester County. Her father was president of a magazine publisher, and her mother served as conservation chair of the Garden Club of America.

At a 1941 Christmas dance, she met her future husband.

Barbara Bush waited for him at Smith College as he flew combat missions in World War II as the Navy's then-youngest pilot.

They married in January of 1945 and moved to Texas. George Bush worked in oil. The young family moved frequently.

She cared for what would be six children, including one who died in childhood — a harrowing moment that she later said unleashed her prematurely grey hair.

A failed bid for Senate in 1964 led to a successful Congressional run two years later.

After losing a second Senate bid, Bush became Ambassador to the United Nations, chief envoy to China, chairman of the Republican National Committee, and CIA director.

Then, Barbara Bush became second lady.

It's not normally a post inviting controversy.

But after Democratic nominee Geraldine Ferraro, a Queens congresswoman, questioned whether the wealthy Bushes could relate to average Americans, Barbara Bush reportedly responded to a reporter: "Ferraro is a word I can't say, but it rhymes with rich."

She later said she meant witch, but apologized, and Ferraro accepted.

Barbara Bush also indicated she was in favor of abortion rights, and favored gun control. But amid an increasingly conservative Republican Party, she kept those views largely quiet until after her husband left office.

Instead, as first lady, she saw her role as more traditional, celebrating Thanksgiving with troops in Saudi Arabia during the first Iraq War, flanking her husband when he announced Clean Air Act amendments.

In 1989, the First Family's springer spaniel Millie gave birth to puppies. The following year, the dog's-eye view that Barbara Bush ghost-wrote hit stores.

Literacy advocacy became a cause for her namesake foundation, which raised millions to teach adults and kids alike to read.

"I came from a reading family," she said in an interview. "My father was in the publishing business, they read to me, I read to the children."

And Americans read her memoir, a bestseller in which she talked of differences with her husband and debilitating depression.

The book emerged two years after her husband lost the White House to Bill Clinton, whose wife, Hillary, got Barbara Bush's vote in 2016.

That election also saw her son Jeb lose in the Republican primaries.

In failing health in recent years, she had previously appeared publicly in Texas and the family's Maine estate, a fishing rod in-hand.

In addition to her children, grandchildren, and great-grandchildren, her husband survives her.

Their 73-year-long marriage is the longest in presidential history.

Reactions to Bush's death

"As a wife, mother, grandmother, military spouse, and former First Lady, Mrs. Bush was an advocate of the American family. Amongst her greatest achievements was recognizing the importance of literacy as a fundamental family value that requires nurturing and protection. She will be long remembered for her strong devotion to country and family, both of which she served unfailingly well. The President and First Lady's thoughts and prayers are with the family and friends of Mrs. Bush," President Trump said in a statement.

"Barbara Bush was the rock of a family dedicated to public service, and our thoughts and prayers are with both Presidents Bush and the entire Bush family tonight. We'll always be grateful to Mrs. Bush for the generosity she showed to us throughout our time in the White House, but we're even more grateful for the way she lived her life – as a testament to the fact that public service is an important and noble calling; as an example of the humility and decency that reflects the very best of the American spirit," former President Barack Obama said in a statement.