The risk of developing dementia may be much higher than previously thought, according to a study published Monday in the journal Nature Medicine.
Previous studies estimated that around 14% of men and 23% of women would develop dementia during their lifetime. The new study raises that estimate to 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, who was not involved in the research. .
The increase in the risk and number of people with dementia – which researchers say will have doubled by 2060 – is mainly due to people living longer than previous generations, according to Dr. Josef Coresh, director of the Institute of Optimal Aging from New York University Grossman School of Medicine
“The mere fact that the population is going to age will mean that the number of dementia cases will double overall,” Coresh said. Among black Americans, for whom the risk is highest, the number of cases is expected to triple, he added.
About 10% of Americans over age 65 have been diagnosed with dementia, according to the Centers for Disease Control and Prevention (CDC).
The study involved more than 15,000 people in the United States who were followed for more than two decades. About a quarter of the participants were black and more than half were women, two groups at high risk.
The average lifetime risk of dementia for a 55-year-old person is 42%, but it was not the same at all ages, the report added. Most of it occurred after the age of 85. Between ages 55 and 75, the average risk of developing dementia was 4%, according to the study. At age 85, the risk was 20%. The risk did not reach 42% until age 95.
For African Americans and women, the risk was higher, but the pattern was similar.
At age 75, the risk was 7%, almost double the average. At 85, the risk increased to 28% and at 95 it was 42%. For women, the risk was 3% at age 75, 21% at age 85, and 48% at age 95.
“We have to think about the causes of this risk and how to prevent it,” said Coresh.
Previous research has found that the elevated risk may be due to higher rates of diabetes and hypertension among black Americans, largely due to inequalities in access to health care, and structural racism that can cause stress, which which increases the risk of dementia.
Much of the high risk detected in women can be attributed to the fact that, on average, they live longer than men, but that is not all. A genetic variant called APOE-4, which increases the likelihood of Alzheimer’s, the most common type of dementia, may increase the risk more in women than in men in certain age groups. Research on the influence of pregnancy on the risk of dementia has produced mixed results.
Why is the risk of dementia higher than before?
Previous studies suggested that approximately 14% of men and 23% of women would develop dementia during their lifetime. According to experts, the 42% risk found by these researchers is much higher, which can be explained by several factors.
Previous studies, such as the Framingham Heart Study and the Rotterdam Study, both published in the late 1990s, included a less diverse group of participants, all of whom lived in the same city. It is a problem, some experts said, ubiquitous in dementia research.
Dr. Monica Parker, associate professor of neurology at Emory University’s Goizueta Alzheimer’s Disease Research Center, sees patients as a primary care physician at the Good Samaritan Health clinic in Atlanta. Many of them are immigrants and do not speak English.
“Most of our academic health centers are not prepared to care for people who do not speak English,” which means that this sector of the population is often left out of research, explained Parker, who also chairs the medical advisory board. scientist and memory assessment scientist at the Alzheimer’s Foundation of America and has been a paid educational consultant for Eli Lilly, Biogen and Eisai, three companies that make Alzheimer’s drugs.
Other studies may have had difficulty maintaining contact with participants who developed dementia, Huey added.
The researchers in this study, however, “did a very good job of following people,” he said.
Finally, much of the data that exists on dementia focuses on a single type: Alzheimer’s disease.
“Saying dementia is like saying cancer. There are many subtypes,” said Michelle Mielke, professor and chair of Epidemiology and Prevention at Wake Forest University School of Medicine in North Carolina.
Alzheimer’s disease is the most common type of dementia, accounting for up to 80% of cases, according to CDC data. However, according to Mielke, research that only takes into account Alzheimer’s disease leaves out dementia caused by other conditions, such as cardiovascular and neurological diseases.
“All diseases related to aging are increasing with the aging of the population, we are seeing an increase in strokes, and that is going to be a risk factor for vascular dementia,” he added. “Sometimes we are victims of our own success. “People are living longer with many more comorbidities.”
These comorbidities, such as stroke, hypertension and type 2 diabetes, increase the risk of dementia. It’s also likely that more cases will be diagnosed that would have previously gone undetected, according to 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 that include screening for cognitive impairment.
“If more people go to a doctor’s office, it is possible that more screening tests will be done and more cases will appear,” Whitehouse said.
Although the new data is stark compared to previous figures, Dr. Andrea Bozoki, chief of the division of cognitive and behavioral neurology at the University of North Carolina School of Medicine, added that people should remember that not everything the world will develop dementia in old age.
“Less than half of people who reach the age of 95 will suffer from dementia,” he stated. “Dementia is not an inevitable part of aging, no matter how old you are.”
Although 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 many ways to reduce the risk of dementia.
“Making sure that hypertension and diabetes are controlled will certainly help cognition,” said Mielke, of Wake Forest University.
Getting good sleep, including treating problems such as sleep apnea, can also reduce the risk of dementia, as can a healthy diet. As a general rule, what is good for the heart is also good for the brain, and vice versa.
“We know that changes in vascular risk factors that help the heart also help the brain,” Coresh said.