Rosalynn Carter, the wife of former President Jimmy Carter, has been diagnosed with dementia, the family announced this week.

At 95 years old, Carter is part of a cohort known as the "oldest old" — one in which rates of dementia are starkly higher than other age groups.

Among adults age 65 and older, 10% of them have dementia and 22% have mild cognitive impairment, found a 2022 Columbia University study published in the journal JAMA Neurology.

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Among people between 65 and 69, 3% are diagnosed with the condition. Dementia rates spike to 35% for people age 90 and older, per the study’s findings.

Looking at the population of elderly people, some studies have broken it down into three groups: the "youngest old" between the ages of 65 and 74 years of age, the "middle old" between 75 and 84, and the "oldest old," who are 85 and over.

The U.S. Census Bureau, however, has claimed that the "oldest old" should include people who are 90 or older, as they represent the quickest-growing part of the U.S. population and are expanding faster than the 85- to 89-year-old segment, according to a 2013 study published in the journal Continuum.

It can be challenging to diagnose dementia in advanced ages, as the symptoms can in many ways overlap with normal changes that occur as someone ages, noted Dr. James Pratty, an assistant clinical professor of psychiatry at the University of California Riverside School of Medicine.

"It’s also further made difficult because some of the symptoms of dementia, including memory loss, can be caused by medical and psychiatric conditions that may cause confusion, which can mimic dementia," he explained to Fox News Digital. 

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These conditions can include depression, dehydration, electrolyte abnormalities and urinary tract infections, Pratty added.

The progression of dementia decline, or the rate at which it occurs, becomes much more rapid in individuals over age 65 versus those who are younger, Pratty explained.

"The progression of the disease also very much depends upon the type of dementia," he went on. "Vascular dementia, Lewy body dementia and Alzheimer’s disease each can progress at a different rate — and all of them will decline more rapidly when the onset is significantly late in life."

Another risk factor for those facing dementia in their 90s is that the typical medical interventions don’t prove to be as effective in this population, Pratty noted. 

Individuals age 90 or older are also at a greater risk of developing problems with balance, coordination, vision and hearing, he added. 

"This powerful combination increases the risk of falls," he said. 

Some of the more common risk factors of dementia also come into play for the "oldest old," Pratty said.

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These include social determinants of health, which are the conditions in the environment that affect a wide range of medical conditions, functional abilities and quality-of-life outcomes, he explained.

"Social isolation and poor diet, along with a lack of regular exercise, can also increase one’s risk of developing dementia as they age," Pratty said. 

In addition, a number of chronic health issues — such as diabetes, high cholesterol, hypertension and depression — can increase dementia risk.

People 85 and older are also more susceptible to dementia if they use certain substances, the doctor noted.

"The two most common substances that can cause damage to blood vessels in the aging brain or cause direct damage to the brain cells include alcohol and smoking cigarettes," Pratty said. 

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For those who have a family history of dementia, the risk also increases as they grow older.

"In addition, patients who have experienced head injury or had a stroke have an increased risk of developing dementia," Pratty added.

Rosalynn Carter "continues to live happily at home with her husband, enjoying spring in Plains (Georgia) and visits with loved ones," according to a family statement published on The Carter Center website.

Carter has long served as an advocate for mental health, working to improve access to care and to reduce the stigma surrounding it.

"We recognize, as she did more than half a century ago, that stigma is often a barrier that keeps individuals and their families from seeking and getting much-needed support," the statement continued. 

"We hope sharing our family's news will increase important conversations at kitchen tables and in doctor’s offices around the country."

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