Former US First Lady Rosalynn Carter, the wife of ex-President Jimmy Carter, has entered hospice care at home at the age of 96, the Carter Center says.
"She and President Carter are spending time with each other and their family," the organisation said in a statement, requesting privacy.
Mrs Carter was diagnosed with dementia in May. Her husband, 99, has been in hospice care since February.
The longest-married first couple marked their 77th wedding anniversary in July.
President Carter served one term in office from 1977-81.
Since leaving the White House, he and his wife have remained active, carrying out humanitarian work through the Carter Center.
They live together in the same one-storey house in Plains, Georgia, the small town where they were both born, wed and lived before Mr Carter's political career began.
Their last public appearance came in September when the couple delighted hometown fans by riding in a vehicle through the Plains Peanut Festival, a nod to their past as peanut farmers.
The Carters' public health outreach and disease-eradication efforts have gained prominence amid their health challenges.
In particular, Mrs Carter has been a huge advocate for mental health treatment and caregiving, with a focus on reducing the stigma against mental illness.
As first lady, she was the honorary chair of the President's Commission on Mental Health and helped pass a bill to increase spending on mental health services for disadvantaged communities.
After leaving office, she founded the Rosalynn Carter Institute for Caregivers, which offers support, research and funding to Americans who care for aging family and loved ones.
In August, the Carter Center revealed Mrs Carter had a quiet 96th birthday celebration at home with her husband and other family members,
The organisation said she ate cupcakes and peanut butter ice cream, and released butterflies into the garden.