The risk of developing dementia is higher than previously believed, with the number of cases expected to double in the coming decades, according to a new study. Data indicates that more than two out of five Americans over the age of 55 may develop dementia during their lifetime.

A recent study, published on January 13 in the medical journal Nature Medicine, estimates that approximately 42% of Americans aged 55 and older will experience dementia at some point in their lives, assuming they live long enough. In 2020, there were approximately 514,000 new cases of dementia in the United States, but this number is projected to increase to nearly one million new cases annually by 2060.

This sharp rise is largely attributed to the aging of the “baby boomer” generation, the youngest members of which are now over 60. By 2040, all individuals from this generation will be at least 75 years old, an age at which the risk of dementia increases significantly.

Professor David Tanne, Director of the Stroke and Cognitive Neurology Institute at Rambam Health Care Campus and Chair of the Israeli Society for Cognitive Neurology, highlights the significance of these findings: “This trend is not unique to the United States—it is also highly relevant to the Israeli population. In Israel, we rely on surveys based on documented dementia diagnoses in the electronic health records of health maintenance organizations (HMOs).

“However, these data represent only the tip of the iceberg. The new findings suggest that the lifetime risk of developing dementia in Israel is much higher than previously estimated, and the number of cases is also expected to double. These findings underscore the urgent need for national planning and preparedness, as well as practical measures for prevention and early, accurate diagnosis. The encouraging news is that much can be done—there are numerous steps that can significantly reduce the burden of dementia in Israel.”

The study assessed the cumulative lifetime risk of dementia using data from the ARIC (Atherosclerosis Risk in Communities) study, a long-term, community-based cohort study conducted in the United States. The research included 15,043 participants aged 55 and older who were free of dementia at the start of the follow-up period. The study population consisted of 26.9% Black participants, 55.1% women, and 30.8% individuals carrying at least one copy of the APOE ε4 allele, a well-established genetic risk factor for dementia.

The research methodology involved a median follow-up period of 23 years (ranging from 16 to 27 years) during which participants were monitored through cognitive assessments, telephone interviews, medical records, and death certificates. The findings revealed that 42% of participants aged 55 and older developed dementia during their lifetime, with higher risks observed among women (48% versus 35% in men), African Americans (44% versus 41% in whites), and APOE ε4 carriers (59% for those with two copies of the allele versus 39% for non-carriers).

“Dementia does not occur overnight—it is a gradual process that unfolds over many years,” explains Professor Tanne. “It is also important to clarify that dementia is not a single disease, but rather an umbrella term encompassing a cluster of conditions that impair memory, cognitive skills, and behavior. When the impairment becomes severe enough to interfere with daily functioning, it is classified as dementia. In contrast, when there is a decline in memory and cognitive skills that is milder and does not disrupt daily life, it is referred to as ‘mild cognitive impairment.'”

The study also found that the risk of dementia varies with age: only 17% of cases are diagnosed before the age of 75, with the average age of diagnosis being 81. Among women, the lifetime risk of developing dementia is 48% (approximately one in two women), compared to 35% among men (approximately one in three men), primarily due to women’s longer life expectancy.

The most common cause of dementia is neurodegenerative diseases, particularly Alzheimer’s disease, followed by vascular brain diseases and stroke. Major risk factors for dementia include advanced age, genetic predisposition (e.g., APOE ε4), cardiovascular diseases, hypertension, diabetes, and obesity. Additionally, conditions such as untreated hearing loss and head injuries elevate the risk.

“In older age, most cases of dementia result from a combination of factors, such as vascular brain disease co-occurring with neurodegenerative processes that damage brain tissue,” Professor Tanne explains. “Since vascular brain diseases are a significant contributor to accelerated cognitive decline, maintaining the health of cerebral blood vessels and preventing cardiovascular disease is crucial.”

Maintaining brain health can be achieved through the management of modifiable risk factors, such as cardiovascular diseases, hypercholesterolemia, and hypertension. Lifestyle interventions, such as avoiding smoking, reducing sedentary behavior, maintaining a healthy weight, engaging in regular physical activity, participating in mentally stimulating activities, and fostering supportive social connections, can significantly enhance cognitive health over time.

Professor Tanne emphasizes that while age and genetic predisposition are uncontrollable factors, there are many actionable steps to reduce the risk of dementia:

According to researchers, only about 20% of adults in the United States meet healthy lifestyle targets, and merely 30% of older adults with hearing loss use hearing aids. The study also highlights significant racial disparities, with dementia diagnosis rates being higher and onset earlier in Black adults than in white adults. These disparities are attributed to structural racism, unequal access to education and nutrition, and healthcare inequities.

Professor Tanne also highlights higher dementia rates among the Arab population in northern Israel, stressing the need for culturally tailored interventions: “We provide early diagnostic services for dementia across northern Israel and have found that dementia rates among the Arab population are higher compared to the Jewish population. Dementia tends to appear at younger ages, and patients often seek medical attention at more advanced stages of the disease. Our goal is to understand the contributing factors and provide culturally sensitive care.”

He adds, “The elevated dementia rates in the Arab population may stem from a combination of factors, including a higher prevalence of untreated cardiovascular diseases, potential genetic factors, and lifestyle patterns. In this population, there is a need for Arabic-speaking neurologists and culturally appropriate services.”

Professor Tanne underscores the growing burden of dementia as life expectancy increases: “The current burden of dementia is significant, and similar to the United States, it is expected to rise sharply in Israel. As we improve our management of chronic diseases and cancer, and life expectancy continues to increase, addressing dementia and its consequences will become a central challenge in the coming years.”

However, Professor Tanne notes that recent research suggests that approximately 50% of dementia cases are preventable or at least delayable. He adds that delaying the onset of dementia by just five years could reduce the prevalence of dementia in Israel by nearly half, an outcome with profound implications for healthcare systems, the economy, and society.

“When half of the cases are preventable or delayable, effective prevention planning becomes critical,” he states. “We can achieve this through primary prevention—promoting brain-healthy lifestyles and managing cardiovascular risk factors—as well as early and accurate diagnosis of cognitive decline before dementia develops.”

Recent diagnostic criteria published by the American Alzheimer’s Association advocate for the use of biological markers rather than relying solely on cognitive testing. Furthermore, new biological therapies designed to slow disease progression have become available, with additional drugs in advanced stages of development. Researchers stress that public policy must prioritize prevention and healthy aging, as dementia is not inevitable. Through daily preventive measures, it is possible to significantly enhance quality of life and cognitive health in older age.

Professor Tanne concludes: “We have an opportunity to act strategically at the national level, implementing measures such as promoting primary prevention to maintain brain health, early and precise diagnosis of cognitive decline, and providing tailored treatment for high-risk populations. While most dementia cases occur in older age, the actions required for national planning must begin decades earlier, necessitating a fundamental shift in mindset.”