Former First Lady Rosalynn Carter is battling dementia, according to the Carter Center, which issued a statement on Tuesday."She continues to live happily at home with her husband, enjoying spring in Plains and visits with loved ones," according to the statement.The 95-year-old has been known for her work in her duties as first lady, as well as in the charitable work she did long after her husband left the Oval Office. She's been active in various philanthropic causes, including mental illness, homelessness, and human rights.Tuesday's announcement comes months after former President Jimmy Carter, 98, began undergoing hospice care at the couple's home in Plains, Georgia.Video above: Jimmy and Rosalynn Carter spent decades building houses for Habitat for HumanityLast week, the couple's grandson, Jason Carter, said the former president and first lady are resting comfortably at home."They're down in Plains," Carter said of his grandparents. "They're together and they've been together for 70-plus years. They're coming to the end. He's going to be 99 in October, but right now, it's sort of the perfect way for them to spend these last days – together at home in Plains."In her role as first lady, Carter helped the president write his speeches and advise him on key issues. She worked alongside her husband for decades, helping out with his presidential campaigns as well as his preceding campaigns for state senator and governor of Georgia. Rosalynn Carter also traveled across the country and the world as first lady in support of breaking mental health stigmas.Video above: Carter's grandson gives update"Since 1971, Rosalynn had been a champion of mental health issues, and her leadership in this cause continues even now," President Carter wrote in "White House Diary," an annotated account of his time in the White House published in 2010.Carter continued, "She mounted a worldwide crusade to reduce the stigma associated with mental illness and helped persuade the World Health Organization and Centers for Disease Control to include mental health on their agendas."The couple has been married for nearly 77 years. Dementia is a broad term for an impaired ability to remember, think and make decisions, according to the CDC. People with dementia may have trouble with memory, attention, communication, judgment and problem-solving, and visual perception beyond typical age-related vision changes.Dementia is not a normal part of aging, according to the National Institute on Aging, but about one-third of all people age 85 and older may have some form of dementia.CNN contributed to this report.