New cases of dementia will double by 2060, when 1 million U.S. adults are projected to develop the memory-robbing condition each year, according to a sobering new study published Monday in the journal Nature Medicine.
The new analysis shows that the risk a person faces over their lifetime is higher than some previous estimates: After age 55, 4 in 10 adults are likely to develop some form of dementia. That’s in part because the new analysis is based on decades of close follow-up, including regular cognitive assessments, of a racially diverse group of people – a quarter of whom were Black and face an increased risk of dementia.
“If you start at age 55 and go forward until your 95th birthday, there are two options: You die before dementia, or you get to dementia before death,” said Josef Coresh, founding director of the Optimal Aging Institute at the New York University Grossman School of Medicine. From age 55 to 75, he noted, the risk of developing dementia is only about 4 percent. That increases substantially over the next two decades, particularly after people’s 85th birthday.
The new analysis relied on the long-running Atherosclerosis Risk in Communities Study that started in 1987 to track cardiovascular risk, funded by the National Institutes of Health. The population the researchers followed includes more than 15,000 people from Maryland, North Carolina, Mississippi and Minnesota. The geographic and racial diversity of the sample helped underscore the risk inequities: Black people, women and carriers of a gene variant called APOE4 that’s linked to Alzheimer’s disease are more likely to develop dementia.
But the increase in the projected number of people developing dementia is, Coresh said, driven by the aging population. More people are projected to be alive in the age brackets when the condition is most common over time.
Theo Vos, an epidemiologist and emeritus professor at the University of Washington who was not involved in the study, said that dementia is a difficult condition to consistently measure, in part because norms around listing it as the cause of death have varied by country and changed over time. There is also variability in the criteria and tests used to deem someone as having dementia.
“The strength of this study is that they followed people up over time, and they kept probing for signs that would confirm, or not, a diagnosis of dementia. That’s a strength because with dementia being a progressive disease, it may be hard in the beginning to say is this, or is this not dementia. But give it another three, four, five years and it’s pretty obvious whether it is or is not,” Vos said.
The urgency to prevent dementia
What should give people some hope is that there is increasing evidence that this fate isn’t written in stone.
Research commissioned by medical journal The Lancet last year found that 45 percent of cases of dementia globally are potentially preventable. Managing the risk factors that contribute to heart disease, including controlling and preventing high blood pressure, high cholesterol, obesity and diabetes can also help protect against dementia. Treating hearing loss and avoiding social isolation can be protective. Avoiding smoking and excessive alcohol consumption can also reduce the risk.
“That tends to reduce the risk at any given age – people get more years free of dementia,” Coresh said.
Maria Carrillo, chief science officer of the Alzheimer’s Association, which was not involved in the study, called it a wake-up call. She said a study set to be released this summer is rigorously testing specific lifestyle changes to see if they protect cognitive function in more than 2,000 older adults.
“In the U.S., we live in a very unique situation. The disparities … that impact health are fairly significant,” Carrillo said. “It sounds very daunting. What I can say about the numbers, though, is that this is also a time where we’re learning so much more about those underlying causes – and that many of them actually can be mitigated.”