Study Reveals Higher Dementia Risk Than Previously Estimated

Feature and Cover Study Reveals Higher Dementia Risk Than Previously Estimated

The likelihood of developing dementia during one’s lifetime may be significantly greater than earlier estimates, according to a study published in Nature Medicine. Past research suggested that 14% of men and 23% of women would develop dementia. The new findings place this lifetime risk at approximately 42% for both genders.

Dr. Ted Huey, director of the memory and aging program at Butler Hospital in Rhode Island, remarked, “I think this is going to be a very important study, and I think it is going to change the way we look at dementia.”

Increasing Cases with Longer Lifespans

The study, led by Dr. Josef Coresh, director of the Optimal Aging Institute at NYU Grossman School of Medicine, highlights that the rising number of dementia cases correlates with increased life expectancy. “Just the fact that the population is going to get older will mean the number of dementia cases will double overall,” Coresh explained. Among Black Americans, who face a higher risk, cases are expected to triple by 2060.

Currently, about 10% of Americans aged 65 and older have dementia, with nearly 7 million people in the U.S. affected by Alzheimer’s, the most common type.

The research tracked over 15,000 U.S. participants for more than two decades, with around a quarter of them being Black and more than half women, both groups known for elevated dementia risks.

Lifetime Dementia Risk

On average, a 55-year-old has a 42% risk of developing dementia during their lifetime. However, this risk is age-dependent. From ages 55 to 75, the likelihood is 4%. By 85, the risk rises to 20%, and it reaches 42% by age 95.

For Black Americans, the risk increases more sharply:

  • 7% by age 75,
  • 28% by age 85,
  • 42% by age 95.

Similarly, women face higher risks, with estimates of:

  • 3% by age 75,
  • 21% by age 85,
  • 48% by age 95.

“We need to think about the causes for this risk and how to prevent it,” Coresh emphasized.

Factors Behind Increased Risk

Several factors contribute to the heightened dementia risk, especially among Black Americans and women. Elevated rates of diabetes and hypertension among Black Americans, often linked to unequal healthcare access and systemic racism, are key contributors. Stress from structural inequities further exacerbates the problem.

For women, longer life expectancy partially explains their higher risk, but other factors, such as genetic predispositions, also play a role. A genetic variant called APOE-4, associated with Alzheimer’s, may increase women’s susceptibility to the disease more than men’s. Researchers are also exploring whether pregnancy could influence dementia risk, though findings remain inconclusive.

Why Are the Numbers Higher Now?

The 42% lifetime risk identified in this study is notably higher than earlier estimates, which ranged from 14% to 23%. This discrepancy can be attributed to differences in study design and population diversity.

Older studies, such as the Framingham Heart Study and the Rotterdam Study from the late 1990s, were geographically limited and included less diverse participants. This lack of diversity is a recurring issue in dementia research, according to experts.

Dr. Monica Parker, a neurology associate professor at Emory University’s Goizueta Alzheimer’s Disease Research Center, highlighted the challenges of inclusivity. “Most of our academic health centers aren’t set up to see non-English-speaking people,” she noted, adding that this segment of the population is often excluded from research.

Another reason for the higher risk found in the new study is improved participant follow-up. Dr. Huey acknowledged, “The researchers in this study did a very good job of following people.”

Additionally, most dementia research focuses on Alzheimer’s disease, leaving out other forms of dementia caused by cardiovascular or neurological conditions. “Saying dementia is like saying cancer. You have a lot of subtypes,” explained Michelle Mielke, a professor at Wake Forest University School of Medicine.

The Role of Comorbidities

The aging population brings an increase in age-related diseases like stroke, which heightens the risk of vascular dementia. “Sometimes we are a victim of our own success. People are living longer with a lot more comorbidities,” Mielke noted. These comorbidities, such as high blood pressure, diabetes, and stroke, significantly elevate dementia risk.

Another contributing factor is improved screening. Since 2011, Medicare has reimbursed providers for annual wellness visits, which include cognitive decline screenings. Dr. Peter Whitehouse of Case Western Reserve University observed, “If more people are coming into a physician’s office, they may be screening more, and more cases will show up.”

Dementia Is Not Inevitable

Despite the stark numbers, experts caution against assuming that dementia is an unavoidable part of aging. “Less than half of people who make it to age 95 will have dementia,” said Dr. Andrea Bozoki, division chief of cognitive and behavioral neurology at the University of North Carolina School of Medicine.

While some risk factors, like genetics and air pollution exposure, are uncontrollable, there are ways to mitigate risk. Controlling hypertension and diabetes can help, as can maintaining good sleep hygiene and addressing conditions like sleep apnea.

A healthy diet also plays a significant role. “As a rule of thumb, what’s good for the heart is also good for the brain,” Coresh remarked. “We know that the vascular risk factor modifications that help your heart also help your brain.”

Hope for Prevention

The study’s findings highlight the importance of prevention and early intervention. Researchers and healthcare providers stress the need to address underlying conditions, particularly in vulnerable populations. Increasing access to care and targeting modifiable risk factors can help reduce the growing burden of dementia.

As Bozoki pointed out, “Dementia is not an inevitable part of aging, no matter how old you are.”

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