Joan Presky is worried about dementia. Her mother lived with Alzheimer's for 14 years. The last seven were in Memory Care residences, and their mother's grandfather also developed dementia.
“I'm 100% sure this is my future,” said Presky, 70, a retired lawyer in Thornton, Colorado.
Last year, she spent almost a day with a neuropsychologist and received extensive reviews. The results show that her short-term memories are doing well – she turns out to be “shocking and comforting” – and she tested above average in all cognitive categories.
She's not relieved. “We saw what Alzheimer's disease is,” she said of her mother's long decline. “The memories of what she went through are profound to me.”
The outlook for dementia, covering Alzheimer's and many other cognitive impairments, is scaring Americans, and is attracting public attention as recent research predicts a sharp rise over the next 30 years.
The researcher's findings published in January on Nature Medicine appeared as a joke in the Saturday Night Live weekend update segment.
“Dementia is a catastrophic condition and is highly related to the oldest age,” said Dr. Joseph Kosh, director of the Institute for Optimal Aging at NYU Langone Health and senior author of the study. “The Earth is getting older.”
The findings are currently being challenged by other dementia researchers. Other dementia researchers say that while the increase is coming, it will be much smaller than Dr. Coresh and his co-authors predicted.
Using data from around 15,000 Americans over 55 years of age collected at four research clinics across the country from 1987 to 2020, Dr. Coresh's team projected a much higher risk of dementia than previous studies.
High lifetime numbers reflect the reliance on research on a more diverse sample than previously used by researchers, said Dr. Coresh, cases of dementia were identified through detailed surveys, regular calls, medical records and death certificates.
The researchers applied risk calculations to the US population, and estimated that the number of people who develop dementia each year will be about doubled by 2060 and about doubled by 2060.
Eric Stallard, biodemography actuary and co-director of the Duke University Aging Research Unit, read the study and thought the team “appeared to be extremely competent at their analysis.”
However, regarding the prediction that cases would double, he assumed that the incidence of dementia would remain stable over the next 40 years, Stallard said.
“The concept that the number of people with dementia doubles over the next 25, 30 or 35 years due to aging in the baby boomer generation, is widespread, and that's wrong,” he added.
He and two other Duke researchers recently published a commentary in Jama, pointing out that the age-specific prevalence of dementia in the country had been steadily decreasing for 40 years.
“If the risk is lower than the risk for parents and this trend continues, we don't see any double or triple predicted dementia,” said Dr. Moolari Drewamy, director of Duke's neurocognitive impairment program and co-author of the Jama article.
To clarify, experts agree that the number of people with dementia will rise in the coming decades simply because disability will rise sharply with age and the number of seniors in the United States will increase.
However, Stallard estimates that this increase will be around 10-25% by 2050.
The Duke Group relies on long-term research on people over the age of 65, with over 21,000 respondents in 1984, approximately 16,000 in 2004, and data from the National Health and Resignation Survey and National Health and Aging Trends Survey.
Their analysis found that, for example, among those aged 85-89, the rate of dementia was approximately 23% in the cohort born in 1905.
By the time Americans born in 1935 reached the late 1980s, about 11% had dementia. The current forecast for people born between 1945 and 1949 is around 8%.
For Dr. Coresh, who had a major interest in individual risk, the assumption that past declines will continue at the current rate “will be large, but it's a very optimistic and dramatic decline,” he said in an email.
However, another longitudinal study of elderly people in the UK and China published in Natural Aging last year, “we also found these significant improvements in a recently born cohort,” said Dr. John Beard, a medical epidemiologist at the School of Public Health at Columbia University.
“We would expect the absolute increase in the number of people with dementia in the United States to be less than we were afraid,” Dr. Beard said.
What has led to the reduction in dementia seen in some European countries? In many cases, the cited explanations include increased levels of education, reduced smoking, improved treatment for high blood pressure and high cholesterol.
The Lancet Committee on Dementia, Interventions and Care has developed a list of 14 modifiable risk factors, including hearing aid use and reducing air pollution.
But the opposite can also happen. Dr. Draiswammy noted that if faster, broader testing increases the number of diagnoses of dementia, or if the definition of dementia is broadened and the speed increases. An increase in life expectancy will have the same effect.
Obesity and diabetes have been more common in recent decades and can lead to dementia, but new drugs that could reduce them could blunt that trend if people were able to get them.
“This is inevitable,” said Dr. Gillivingston, a psychiatrist at University College London, who leads the Lancet Committee. “It depends on what we do.”
Public health policies make a big difference, saying, “The United States is in an age where policy is changing dramatically.”
Dementia rates, for example, are “not likely to receive blood pressure treatment and high cholesterol treatment if people have little access to health care,” Dr. Livingston said.
Reducing Medicaid coverage can result. There could be a rollback of environmental policies “if air pollution increases due to fossil fuels.”
Already, dementia suffers much more American population than others, researchers point out. Elderly women and black people face greater risks, along with those carrying the APOE4 gene associated with Alzheimer's disease.
Health disparities could mean “wealthy people have lower rates of dementia” due to new diabetes and obesity medications, Dr. Draiswamy said. “People who can't afford them and are not well-controlled with conditions, make sure their prices go up.”
The debate about the number of elderly people developing dementia in decades and how individuals, families, governments and the health care system respond will likely continue.
That's the same with Presky's fear.
For now, despite her orthopedic issues, she has enrolled in lifelong learning classes, taking walks and yoga classes, listening to podcasts, and reading a lot of history and fiction. She and her husband attend fish concerts in New York theatres and on the West Coast, and soon head to London and Paris.
Still, her advance orders include many provisions regarding dementia. “I remain pessimistic,” she said. Her mother said she was diagnosed at the age of 77.
