In a recent study published in the journal Nature Medicine, researchers estimated the lifetime risk of dementia in the adult (55-95 years) population of the United States (US). They used a competing risks model to calculate lifetime risk and incorporated detailed prioritization methods for dementia diagnosis. They additionally used US Census data to predict the number of US adults who will have dementia in the year 2060 and the relative risk of dementia across different sociodemographic cohorts (sex, ethnicity, and genetics).
Study: Lifetime risk and projected burden of dementia. Image Credit: Orawan Pattarawimonchai / Shutterstock
Study findings revealed that while the average lifetime risk of dementia in elderly US citizens was ~42%, the highest lifetime risks were observed among APOE ε4 carriers (59%), followed by women (48%) and Black populations (44%). Alarmingly, 2060 dementia projections revealed that novel dementia incidence would almost double from current numbers (514,000 per annum [pa] in 2020) to 1 million pa. The growth was most pronounced among individuals aged 75-84 and 85-95 years. These findings highlight the need for policy implementations targeting at-risk populations to curb this impending crisis and enhance healthy aging in years to come.
Background
'Dementia' is an umbrella term for several neurological diseases whose symptoms include declines in cognitive function, especially thinking, memory, and reasoning abilities, substantially impacting daily life. Dementia results from brain damage, which, while not a normal part of the human aging process, increases in likelihood as individuals age. Dementia may also cause notable changes in patients' personalities, moods, and behavior, significantly burdening their families and loved ones.
Dementia is particularly prevalent in the United States – once a rare condition, dementia now affects over 6 million American citizens, presumably due to the nation's aging population. Researchers have estimated that the economic burden of this condition is more than $600 billion annually, necessitating urgent policy implementations to identify high-risk populations, mitigate disease incidence, and enhance healthy aging. Structural factors, including socioeconomic disparities and historical racism, further exacerbate risks in some populations.
While previous studies have identified discrepancies between male and female susceptibility to dementia, their study design utilized small sample sizes, resulting in confounding outcomes between studies. Furthermore, most of these studies focused on White American populations, with other racial and ethnic backgrounds being largely ignored in the literature.
About the study
The present study has two main aims – 1. Compute estimates of lifetime dementia risk in US adults, both for the nation overall, and for specific sociodemographic cohorts, and 2. To predict the novel annual incidence of dementia in the US population over the next 4 decades (until 2060). Study data was acquired from the Atherosclerosis Risk in Communities (ARIC) study comprising three decades of information (1987-2020) from 15,043 participants (55.1% women; 26.9% Black). Participants were screened to ensure that none of them had dementia before age 55 years. Genetic analyses of study participants revealed that 31% of the cohort were carriers of the apolipoprotein E4 (APOE ε4) allele, a genetic trait known to substantially increase dementia risk.
Study findings
Over the ~23 years of the study's follow-up period, 3,252 participants developed dementia, with the median age of dementia diagnosis identified as 81 years. Black Americans and APOE ε4 carriers were diagnosed earlier than other groups (79 years).
Lifetime dementia estimates revealed that 42% of Americans will develop dementia by age 95, substantially higher than previous estimates. Women (48%) are at significantly higher dementia risk than their male counterparts (35%). Black Americans, who historically have been underrepresented in dementia research, face a higher risk (44%) compared to White Americans (41%). The highest population-specific dementia risk was identified in APOE ε4 allele carriers, 59% of whom are expected to develop dementia over their lifetimes.
As expected, age-specific evaluations of dementia risk increase with advancing age – older Americans (>75 years) were more likely to develop dementia compared to their younger (<55 years) counterparts.
When combining lifetime risk estimates derived from these analyses with US census data, researchers discovered that by 2060, the annual incidence of dementia would increase to more than 1 million cases annually, almost double the 2020 incidence rates (~514,000). These projections are substantially higher than any past estimates and highlight the urgent need for mitigatory measures, including citizen education, lifestyle interventions, cardiovascular health optimization, and hearing rehabilitation programs.
Conclusions
The present study evaluated the overall and population-specific (sex, race/ethnicity, and genetics) dementia risk in elderly (55-95 years) American adults. It used these analyses to predict future dementia incidence rates within the country. Study findings revealed alarming outcomes – the overall dementia risk among Americans was 42%, significantly higher than estimated in previous research. Notably, the historically understudied Black American population was at substantially higher dementia risk than their White counterparts (44% versus 41%). Consistent with prior expectations, women depicted higher risk than men (48% versus 35%).
Predictive models revealed that annual dementia incidence would almost double from presence numbers (1 million versus 514,000), emphasizing the need for public health initiatives addressing structural inequalities, improving access to preventive care, and targeting high-risk populations.