by The risk of developing dementia may be much greater than previously thought, according to a study published Monday in the journal Nature Medicine.
Older studies estimate that about 14% of men and 23% of women would develop dementia during their lifetime. The new study puts that estimate higher, at about 42% for both men and women.
“I think this is going to be a very important study, and I think it’s going to change the way we look at dementia,” said Dr. Ted Huey, director of the memory and aging program at Butler Hospital in Rhode Island. was not involved in the research.
Most importantly, the increase in both the risk and number of people with dementia – which researchers estimate will double by 2060 – is the result of people living longer than previous generations, said study leader Dr. Josef Coresh, director of the Optimal Aging Institute at NYU Grossman School of Medicine.
“The mere fact that the population is getting older will mean that the number of cases of dementia will double overall,” said Coresh. Among Black Americans, for whom the risk is higher, the number of cases is expected to triple, he said.
According to the Centers for Disease Control and Prevention, about 10% of Americans over the age of 65 have been diagnosed with dementia. Nearly 7 million people in the US have Alzheimer’s disease, the most common form of dementia.
The study included more than 15,000 people in the US who were followed for more than two decades. About a quarter of participants were black and more than half were women – two groups known to be at increased risk.
According to the study, the average 55-year-old’s risk of developing dementia during their lifetime is 42%, but the risk was not the same at every age. The main focus of this took place after someone’s 85th birthday. According to the study, the average person’s risk of developing dementia between the ages of 55 and 75 was 4%. By the time a person turned 85, their risk was about 20%. The risk did not reach 42% until a person’s 95th birthday.
For black Americans and women, the risk was higher, but the pattern was similar.
Black Americans had a 7% risk at age 75, almost double the average. In 85 years the risk increased to 28%, and in 95 years it was 42%. For women, this risk was 3% at age 75, 21% at age 85 and 48% at age 95.
“We need to think about the causes of this risk and how we can prevent it,” Coresh said.
Previous research has found that increased risk may be caused by higher rates of diabetes and hypertension among Black Americans, largely due to inequities in access to care, and structural racism that can cause stress, putting people at greater risk for dementia.
Much of the increased risk in women can be attributed to the fact that women live longer on average than men – but that’s not the whole story. A genetic variant called APOE-4, which increases a person’s risk for Alzheimer’s disease, may increase the risk more for women in certain age groups than for men. Research into whether pregnancy plays a role in dementia risk has produced mixed results.
Why is the risk of dementia higher than before?
Previous studies suggested that about 14% of men and 23% of women would develop dementia during their lifetime. The 42% risk these researchers found is much higher, which could be explained by several factors, experts said.
Previous studies, including the Framingham Heart Study and the Rotterdam Study, both published in the late 1990s, included a less diverse group of participants, all living in the same city. It’s a problem, experts say, that is pervasive in dementia research.
Dr. Monica Parker, associate professor of neurology at Emory University’s Goizueta Alzheimer’s Disease Research Center, views patients as a primary care provider at the Good Samaritan Health Clinic in Atlanta. Many of her patients are immigrants and do not speak English.
“Most of our academic health centers are not set up to receive non-English speaking people,” meaning this segment of the population is often left out of research, says Parker, who is also chairman of the Alzheimer’s Foundation of America’s medical, scientific and memory screening advisory board and was a paid educational consultant for Eli Lilly, Biogen and Eisai, three companies that make Alzheimer’s disease drugs.
Other studies may have had difficulty keeping in touch with participants who developed dementia, Huey said.
However, the researchers in this study “tracked people very closely,” he said.
Finally, much data in the field of dementia points to only one type: Alzheimer’s disease.
“Saying dementia is like saying cancer. You have many subtypes,” says Michelle Mielke, professor and chair of epidemiology and prevention at Wake Forest University School of Medicine in North Carolina.
According to CDC data, Alzheimer’s disease is the most common form of dementia, accounting for as many as 80% of cases. Research that tracks only Alzheimer’s disease leaves out dementia caused by other conditions such as heart and neurological disorders, Mielke said.
“All age-related diseases are increasing with this aging population, we’re seeing an increase in strokes, and that will be a risk factor for vascular dementia,” she said. “Sometimes we are victims of our own success. People live longer and have many more comorbidities.”
These comorbidities, including stroke, high blood pressure and type 2 diabetes, all increase a person’s risk for dementia. It’s also likely that more cases will be diagnosed that previously went unrecognized, said Dr. Peter Whitehouse, a professor of neurology at Case Western Reserve University in Ohio.
In 2011, under the Affordable Care Act, Medicare began reimbursing providers for annual wellness visits, including screening for cognitive decline.
“If more people come into a doctor’s office, they may screen more and more cases will emerge,” Whitehouse said.
Although the new data is stark compared to previous figures, Dr. Andrea Bozoki, division chief of cognitive and behavioral neurology at the University of North Carolina School of Medicine, said people should remember that not everyone will develop dementia in old age.
“Less than half of people who live to age 95 will have dementia,” she said. “Dementia is not an inevitable part of growing older, no matter how old you are.”
While certain factors that increase the risk of dementia, such as genetics or exposure to air pollution, may be beyond a person’s control, the good news is that there are plenty of ways to lower the risk of dementia.
“Ensuring that high blood pressure and diabetes are controlled will certainly help with cognition,” says Mielke of Wake Forest University.
Getting a good night’s sleep, including treating problems like sleep apnea, can also lower your risk of dementia, as can eating a healthy diet. As a rule of thumb, what’s good for the heart is also good for the brain, and vice versa.
“We know that the changes in vascular risk factors that help your heart also help your brain,” Coresh said.
