Sandra Day O’Connor, the first woman to serve on the U.S. Supreme Court, announced she has been diagnosed “with the beginning stages of dementia, probably Alzheimer’s disease” on October 23.

In an open letter circulated by the Court’s public information office, Justice O’Connor wrote that she would be immediately retiring from public life.

President Reagan nominated Justice O’Connor to the U.S. Supreme Court in 1981, and she was confirmed by the Senate in a vote of 99-0. Previously, she served as Arizona’s assistant Attorney General, and spent two terms as a member of the Arizona State Senate. During her time as a senator, she was elected Majority Leader, the first woman to hold such a position in any U.S. legislative body.

She sat on the bench until 2006, when she retired to care for her husband, John Jay O’Connor, who had Alzheimer’s disease. John Jay O’Connor died in 2009.

Since leaving the Supreme Court, Justice O’Connor, now 88, has devoted herself to “advanc[ing] civic learning and engagement.” In 2010, she founded iCivics, a website that offers free lesson plans and learning games designed for children and adolescents.

Justice O’Connor, who lives in Phoenix, Ariz., remained positive in the face of her diagnosis. “While the final chapter of my life with dementia may be trying, nothing has diminished my gratitude and deep appreciation for the countless blessings in my life,” she wrote.