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Open Access

Peer-reviewed

Research Article

Prevalence and determinants of self-reported all-cause dementia among middle-aged and older adults in the United States: Results from a nationally representative survey

  • Charllote Boateng,

    Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

    Affiliation Division of Epidemiology, Biostatistics, and Environmental Health, School of Public Health, The University of Memphis, Memphis, Tennessee, United States of America

    ⨯
  • Isaiah Osei Duah Junior

    Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

    oseiduahisaiah@gmail.com

    Affiliations Department of Optometry and Visual Science, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, Department of Psychology, John R. and Kathy R. Hairston College of Health and Human Sciences, North Carolina Agricultural and Technical State University, Greensboro, North Carolina, United States of America

    ⨯

Abstract

Dementia encompasses a heterogeneous group of neurodegenerative and cerebrovascular disorders characterized by progressive cognitive decline that impairs memory, executive function, and activities of daily living. Although dementia includes multiple subtypes, nationally representative surveys often do not distinguish among them. Consequently, contemporary population-level estimates of self-reported all-cause dementia and its associated factors among middle-aged and older adults remain limited. This study estimated the prevalence of self-reported all-cause dementia and identified associated factors among middle-aged and older adults in the United States (U.S.). Secondary analyses used data from the National Health Interview Survey (NHIS), a nationally representative survey of the U.S civilian non-institutionalized population. Dementia status was ascertained via self-report using a binary indicator of whether respondents had ever been informed by a physician or other health professional that they had dementia. Survey-weighted descriptive statistics summarized participant characteristics. Univariate and multivariate sequential logistic regression models examined factors associated with dementia, with adjusted odds ratios (aORs) and 95% confidence intervals (CIs) presented in a forest plot. The analytical sample included 130,312 adults aged 40–85 years; 52.3% were women. The prevalence of self-reported all-cause dementia was 1.6% and increased with age and comorbidity burden. In fully adjusted regression models, female sex and overweight or obesity were associated with lower odds of all-cause dementia, whereas older age, lower educational attainment, residence in the west, multimorbidity, depression, anxiety, and enrollment in Medicaid or other public insurance programs were associated with higher odds of all-cause dementia. Approximately 1 in 100 middle-aged and older adults in the U.S reported a diagnosis of dementia. Sociodemographic, educational, physical, and mental health factors were independently associated with dementia. Public health strategies that promote education, improve management of chronic diseases, and strengthen mental health care may help reduce the burden of dementia in this population.

Author summary

Dementia is a health condition that affects memory, thinking, and the ability to carry out everyday activities. It includes several different categories, such as Alzheimer's disease and vascular dementia. However, many large national surveys do not collect information on the specific type of dementia a person has. In this study, we used data from more than 130,000 U.S. adults aged 40–85 years to estimate theburden of self-reported all-cause dementia, meaning any reported dementia diagnosis regardless of the subtype. Participants were considered to have dementia if they reported that a physician or other health professional had told them they had dementia. We found that about one in 100 middle-aged and older adults reported a dementia diagnosis. Dementia was more common among older adults and those with multiple chronic health conditions. Lower educational attainment, residence in the west, depression, anxiety, and enrollment in Medicaid or other public insurance programs were also associated with a greater likelihood of having dementia. In contrast, females and individuals who were overweight or obese had a lower likelihood of reporting dementia. These findings highlight need to improve education, support mental health, prevent and manage chronic diseases throughout life. Together, these strategies may help reduce the burden of dementia and promote healthier aging in the U.S.

Citation: Boateng C, Osei Duah Junior I (2026) Prevalence and determinants of self-reported all-cause dementia among middle-aged and older adults in the United States: Results from a nationally representative survey. PLOS Aging Health 1(3): e0000025. https://doi.org/10.1371/journal.page.0000025

Editor: Goran Miladinov, CRPM, Center for Research and Policy Making, NORTH MACEDONIA

Received: January 9, 2026; Accepted: August 12, 2026; Published: September 10, 2026

Copyright: © 2026 Boateng, Osei Duah Junior. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The dataset used for the analysis of the data is accessible through the NHIS website: https://www.cdc.gov/nchs/nhis/documentation/index.html.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: AOR, Adjusted Odds Ratio; BMI, Body Mass Index; CI, Confidence Interval; COR, Crude Odds Ratio; FPL, Federal Poverty Level; HHS, U.S. Department of Health and Human Services; NHIS, National Health Interview Survey; OR, Odds Ratio; SE, Standard Error; SES, Socioeconomic Status; U.S., United States.

Introduction

Dementia is a disabling and burdensome condition of major public health concern, with a disproportionately high impact among middle-aged and older adults [1]. Globally, the number of people living with dementia is projected to increase from 57.4 million cases in 2019 to 152.8 million by 2050 [2]. Considerable geographic variation exists in both current burden and future projections across Africa [3], Asia [4], Australia [5], Europe [6], and the Americas [7–9]. In the United States, rapid population ageing is expected to substantially increase the number of adults living with dementia, placing growing demands on healthcare systems, long-term care services, and informal caregivers. These demographic trends underscore the need for contemporary, nationally representative estimates of dementia prevalence and associated factors to guide public health planning and resource allocation.

As a heterogeneous group of progressive neurodegenerative and cerebrovascular disorders (such as Alzheimer's disease, vascular dementia, Lewy body dementia, and frontotemporal dementia and others) [1,10], dementia is characterized by progressive cognitive decline that impairs memory, executive function, and functional independence [11,12]. As dementia progresses, individuals experience substantial impairment in daily function [13] reduced quality of life [14,15], diminished employment capacity and social engagement [16–19], and increased dependence on formal and informal care systems [20–22]. These consequences extend beyond the affected individual, but also places significant health, financial, and resource constrain on caregivers and health systems [1,13,23]. The burden of dementia is compounded by age-related reduction in cognitive reserve [24,25], increase in physical frailty [26,27], multimorbidity [28–30], and common mental health conditions, such as depression and anxiety, which are associated with cognitive decline and dementia [29–32].

The Lancet Commission on dementia prevention, intervention, and care identified several potentially modifiable risk factors across the life course, which include limited educational attainment, hearing loss, hypertension, smoking, obesity, depression, physical inactivity, diabetes, excessive alcohol consumption, traumatic brain injury, air pollution, and social isolation [31]. Collectively, these factors account for a substantial proportion of dementia cases worldwide and suggest that effective prevention strategies could meaningfully reduce disease burden [31]. However, the pattern of distribution of these risk factors varies considerably across populations, particularly in socioeconomically diverse countries such as the U.S.

Despite the expanded evidence on dementia, several important epidemiological gaps remain. First, many nationally representative studies in the U.S. have focused primarily on older adults and often excluded middle-aged populations in whom early risk may have been accumulated. Second, previous estimates rely on outdated datasets that may not reflect recent demographic, epidemiological, and healthcare changes. Third, prior studies have often examined risk factors in isolation and failed to consider how sociodemographic disadvantage, behavioral risks, and health conditions jointly contribute to dementia vulnerability. As a result, there remains a limited understanding of how multiple risk domains interact to shape population-level dementia risk across the adult life course [32–35].

Consistent with the two-hit hypothesis, cumulative social disadvantage (first hit) and health-related vulnerability (second hit) will interact to accelerate cognitive decline. Hence, we conjecture that middle-aged and older adults exposed to a greater accumulation of sociodemographic, health-related, and psychosocial risk factors will have a significantly higher likelihood to have had a diagnosis of dementia compared with those with fewer or no such risk exposures. Therefore, this study aimed to estimate the prevalence of self-reported all-cause dementia and identify associated factors among middle-aged and older adults in the U.S. using data from the NHIS. Because the NHIS does not distinguish among dementia subtypes, the present study focuses on overall (all-cause) dementia rather than subtype-specific disease. By providing contemporary nationally representative estimates, this study extends dementia epidemiology beyond traditional elderly-only populations, evaluates the combined contribution of sociodemographic, behavioral, psychosocial, and health-related factors, and strengthens evidence on population-level inequalities in cognitive health. These findings may help inform clinicians, researchers, healthcare administrators, and policymakers in developing equitable strategies for dementia prevention, early identification, and resource allocation within the ageing U.S. population.

Methods

Ethics statement

The study relied on a de‑identified, publicly available dataset and did not involve the collection of any personally identifiable information. Because the data are anonymized and accessible for public research use, this analysis did not need institutional review board oversight. All procedures adhered to ethical standards for secondary data analysis and complied with relevant guidelines for the use of publicly available health survey data.

Study design, population, and setting

This cross-sectional analysis utilized nationally representative data from the NHIS across six annual survey waves (2019–2024). The NHIS is a continuous population-based surveillance system that collects comprehensive information on health conditions, health behaviors, healthcare access and utilization, insurance coverage, and preventive health practices among the U.S. civilian non-institutionalized population. The pooled analytic sample included 130,312 adults, decompose of 22,345 participants from the 2019 wave, 23,029 from 2020, 20,886 from 2021, 19,706 from 2022, 21,073 from 2023, and 23,273 from 2024. To ensure consistency across survey cycles, variables were harmonized using standardized definitions and coding procedures. All analyses incorporated NHIS-provided sampling weights, primary sampling units, and strata to account for the complex survey design and generate nationally representative estimates. These survey weights address differential probabilities of selection, nonresponse, and post-stratification adjustments to U.S. population benchmarks, thereby ensuring valid variance estimation and population-level inference across survey years.

Data source

Data were obtained from the NHIS, a nationally representative survey of the civilian, non-institutionalized U.S. population conducted annually by the National Center for Health Statistics (NCHS) within the Centers for Disease Control and Prevention (CDC) since July 1957. In particular, the NHIS employs a stratified, multistage probability sampling design with clustering and oversampling of Black, Hispanic, and Asian populations to produce nationally representative estimates. Data are collected using computer-assisted personal interviewing (CAPI); however, in response to the COVID-19 pandemic, telephone interviews replaced most in-person interviews after the first quarter of 2020.

This study utilized six consecutive years of NHIS public-use data (2019–2024). These survey years were selected because the NHIS underwent a major redesign in 2019 and introduced a question on physician-diagnosed dementia, including Alzheimer's disease, in the Sample Adult questionnaire. The NHIS provides comprehensive information on sociodemographic characteristics, health conditions, healthcare access and utilization, disability and functional status, and health-related behaviors. Data for the present study were primarily derived from the Sample Adult questionnaire, which contains information on dementia diagnosis, sociodemographic factors, and chronic health conditions.

Measures

Main outcome

The primary outcome was self-reported all-cause dementia, assessed using a binary indicator of whether respondents had ever been informed by a doctor or other health professional that they had dementia. Participants who reported a dementia diagnosis were classified as having self-reported dementia (Yes), whereas those who did not report such a diagnosis were classified as not having dementia (No). Because the NHIS does not collect information on dementia etiology or subtype, including Alzheimer’s disease, vascular dementia, Lewy body dementia, or frontotemporal dementia, the outcome represents all-cause dementia and does not permit differentiation among specific dementia subtypes.

Independent predictors

The main independent variable was comorbidity burden, which captured the number of chronic conditions each respondent reported. Chronic illnesses were identified through self-reported physician diagnoses and included hypertension, diabetes, arthritis, asthma, cancer, and coronary heart disease. Based on these conditions, comorbidity burden was grouped into three categories: (i) no chronic conditions, (ii) one chronic condition, and (iii) multimorbidity, defined as two or more chronic conditions. Mental health status was also included as a key independent variable and was measured using self-reported current or past diagnoses or symptoms of depression or anxiety, with respondents reporting either condition classified as having mental health issues. A range of demographic, socioeconomic, and contextual covariates previously associated with health outcomes and healthcare use were also incorporated, including (i) age, categorized into middle-aged, young-old, and old-old adults to capture differences in aging and health-seeking behavior; (ii) sex, classified as male or female; (iii) race and ethnicity, grouped as White, Black or African American, Asian, and other categories; (iv) socioeconomic status, measured using educational attainment (less than high school, more than high school but less than a bachelor’s degree, and bachelor’s degree or higher) and family income based on the Poverty Income Ratio (below poverty, low, moderate, and high income); (v) marital status, categorized as married, living with a partner, or not in a union (including divorced, widowed, separated, or single); (vi) geographic and structural factors, including type of residence (large central metropolitan, large fringe metropolitan, medium or small metropolitan, and non-metropolitan areas) and U.S. Census region (Northeast, Midwest, South, and West) to account for spatial variation in healthcare access and contextual environments; and (vii) health insurance coverage, classified as uninsured, private insurance, Medicaid or other public insurance, or other forms of coverage. Together, these variables provided a comprehensive framework for examining the relationship between comorbidity burden, mental health, and dementia in a nationally representative sample of U.S. adults.

Statistical analysis

Participant characteristics and the prevalence of self-reported all-cause dementia were summarized using survey-weighted frequencies and percentages. Differences in dementia prevalence across participant characteristics were assessed using survey-adjusted chi-square tests for categorical variables and Wilcoxon rank-sum tests for continuous variables, accounting for the complex NHIS sampling design. Sequential survey-weighted logistic regression models were used to examine factors associated with self-reported all-cause dementia, with results presented as ORs and 95% CIs. Both unadjusted and adjusted models were estimated, and variables included in the final multivariable model were selected based on statistical significance, prior evidence, and theoretical relevance. Sensitivity analyses were conducted to evaluate the robustness of the results, including comparisons between weighted and unweighted estimates and the assessment of alternative categorizations of age and comorbidity burden. Additionally, forest plots were created to visually present the adjusted odds ratios for statistically significant predictors of self-reported dementia. All analyses were executed in R version 4.4.2 using the survey and svyVGAM packages to account for complex survey design features, such as stratification, clustering, and weighting.

Results

Description of the sample

The analytical sample comprised 130,312 adults, of whom 1.6% (n = 2,102) reported a diagnosis of self-reported all-cause dementia and 98.4% (n = 128,210) did not. Slightly more than half were female (52.3%). Participants age ranged from 40 to 85 years and were distributed across middle age (51.0%), young‑old age (34.2%), and old age (14.9%). The sample was predominantly White (79.1%), followed by Black/African American (12.1%), Asian (6.1%), and other racial groups (2.7%). Most had some post-secondary education without a bachelor’s degree (64.0%), while 22.3% held a bachelor’s degree or higher. Nearly two‑thirds were married (62.5%), most lived in metropolitan areas (~85%), and South represented the largest regional proportion (38.1%). Economically, 44.6% were in the high‑income category, whereas 26.1% were in the low‑income or poverty group. Health insurance coverage was high, with 71.5% privately insured and 10.5% uninsured. Comorbidity burden was notable: 36.8% reported two or more comorbidities, compared with 32.8% with none. Regarding behavioral and health characteristics, 87.4% were non‑smokers, 12.7% were current smokers, and overweight and obesity prevalence was 36.3% and 34.8%, respectively. Additionally, 22.7% reported anxiety and 9.2% reported depression, as shown in Table 1.

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Table 1. Baseline characteristics of the sample.

https://doi.org/10.1371/journal.page.0000025.t001

Temporal trends in self-reported all-cause dementia by age and comorbidity

Figure 1 illustrates temporal patterns in self-reported all-cause dementia prevalence by age group (middle-aged, young-old, and older adults) and comorbidity status (no comorbidity, one comorbidity, and two or more comorbidities) from 2019 to 2024. Across all comorbid categories, prevalence in the oldest age group rises from 4.0% in 2019 to a peak of 6.7% in 2021, before fluctuating between 5.2% and 6.6% through 2024. In contrast, the young‑old group increases modestly from 0.3% in 2019 to 1.3% in 2024, while middle‑aged adults remain near 0% throughout the period. A similar pattern emerges among those with one comorbidity, where older adults report the highest levels, increasing from 6.4% in 2019 to 8.8% in 2021, then stabilizing around 7.0–7.2% through 2024. Young‑old adults remain low, ranging from 0.3% to 0.8%, and middle‑aged adults fluctuate narrowly between 0.2% and 0.4%. The effect of multimorbidity is most evident in the two‑or‑more comorbidity group. Older adults report 8.3% in 2019, dipping to 6.5% in 2020, then stabilizing between 6.7% and 7.9% through 2024. Young‑old adults show modest variation (from 1.2% to 1.8%), while middle‑aged adults remain low (between 0.5% and 0.8%). Together, age and comorbidity jointly drive self-reported all-cause dementia risk, with multimorbidity sharply elevating prevalence in older adults while leaving middle‑aged adults largely unaffected (see Fig 1).

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Fig 1. Trends in self-reported all-cause dementia by age group and comorbidity status.

https://doi.org/10.1371/journal.page.0000025.g001

Comorbidity status and self-reported all-cause dementia

There was a graded association between comorbidity and self-reported all-cause dementia (see Fig 2). Individuals without comorbidity consistently report the lowest prevalence of self‑reported dementia, remaining below 1% across all years (ranging from 0.3% to 1.3%). Relative to this group, adults with one comorbidity show clearly elevated prevalence, rising to approximately 1.1–1.5% over time, roughly one to one‑and‑a‑half times higher than those without comorbidity, with a peak around 2021, a dip in 2022, and stabilization thereafter. In contrast, respondents with two or more comorbidities demonstrate the highest prevalence, ranging from 2.3% to 3.1%, which is two to three times higher than individuals without comorbidity. This group shows a sharp decline in 2020, followed by sustained elevations through 2023 and a modest decline in 2024 (see Fig 2).

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Fig 2. Self-reported all-cause dementia by comorbidity status.

https://doi.org/10.1371/journal.page.0000025.g002

Factors related to self-reported all-cause dementia

The univariate logistic regression analysis showed that older age was strongly related to higher odds of self‑reported all-cause dementia. Compared with middle‑aged adults, individuals in the young‑old age group had significantly higher odds of self‑reported all-cause dementia (COR = 4.17; 95% CI: 3.41–5.10; p < 0.001), while those in the old‑age group had markedly elevated odds (COR = 27.97; 95% CI: 23.39–33.43; p < 0.001). Female sex was also related to increased odds of self‑reported all-cause dementia (COR = 1.13; 95% CI: 1.02–1.25; p = 0.021). Educational attainment demonstrated a strong gradient with individuals having less than a high school education exhibiting substantially higher odds of self‑reported all-cause dementia (COR = 4.50; 95% CI: 3.62–5.36; p < 0.001). Comorbidity burden showed a dose‑response relationship, whereby having one comorbid condition increased the odds of self‑reported all-cause dementia more than twofold (COR = 2.58; 95% CI: 2.13–3.14; p < 0.001), while two or more comorbidities increased the odds of self‑reported all-cause dementia nearly sixfold (COR = 5.80; 95% CI: 4.92–6.84; p < 0.001). Depression (COR = 3.96; 95% CI: 3.51–4.47; p < 0.001) and anxiety (COR = 2.55; 95% CI: 2.29–2.84; p < 0.001) were likewise related to higher odds of self‑reported all-cause dementia. Underweight status was related to increased odds of self‑reported all-cause dementia (COR = 2.65; 95% CI: 2.05–3.42; p < 0.001), whereas overweight (OR = 0.57; 95% CI: 0.51–0.65; p < 0.001) and obesity (COR = 0.44; 95% CI: 0.39–0.51; p < 0.001) were related to significantly lower odds of self‑reported all-cause dementia (see Table 2).

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Table 2. Regression analysis of predictors of self-reported all-cause dementia.

https://doi.org/10.1371/journal.page.0000025.t002

After adjusting for covariates, female sex (AOR = 0.44; 95% CI: 0.32–0.61; p < 0.001) and higher BMI status, including overweight (AOR = 0.62; 95% CI: 0.42–0.93; p = 0.021) and obesity (AOR = 0.60; 95% CI: 0.40–0.89; p = 0.012), were related to lower odds self‑reported all-cause dementia. Age remained a significant predictor, with young‑old adults exhibiting higher odds of self‑reported all-cause dementia than middle-aged adults (AOR = 2.18; 95% CI: 1.57–3.02; p < 0.001). Educational attainment also demonstrated a significant relationship with self‑reported all-cause dementia risk; with individuals with more than a high school education but less than a bachelor’s degree (AOR = 2.21; 95% CI: 1.34–3.64; p = 0.002) and those with less than a high school education (AOR = 2.22; 95% CI: 1.19–4.15; p = 0.013) had significantly higher odds self‑reported all-cause dementia. Residence in the West region (AOR = 1.06; 95% CI: 1.25–3.73; p = 0.006) and comorbidity burden where significant predictors, with one comorbid condition (AOR = 2.16; 95% CI: 1.25–3.73; p = 0.006) and two or more comorbidities (AOR = 3.50; 95% CI: 2.07–5.90; p < 0.001) related to a higher odds of self‑reported all-cause dementia. Depression (AOR = 2.32; 95% CI: 1.58–3.40; p < 0.001), anxiety (AOR = 2.01; 95% CI: 1.44–2.82; p < 0.001), and Medicaid or public insurance coverage (AOR = 2.13; 95% CI: 1.09–4.18; p = 0.027) were likewise related to increased odds of self‑reported all-cause dementia (see Fig 3).

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Fig 3. Forest plot illustrates the factors associated with self‑reported all-cause dementia.

https://doi.org/10.1371/journal.page.0000025.g003

Discussion

The aim of this study was to estimate the prevalence of self-reported all-cause dementia and identify associated factors among middle-aged and older adults in the U.S. using NHIS data from 2019–2024. Approximately 1 in 100 adults reported a diagnosis of dementia, with prevalence increasing substantially across older age groups and higher levels of comorbidity burden. After adjustment for potential confounders, female sex and higher BMI categories, including overweight and obesity, were related with lower odds of self-reported all-cause dementia. In contrast, older age, lower educational attainment, residence in the West region, one or more comorbidities, depression, anxiety, and Medicaid insurance coverage were related with higher odds of self-reported all-cause dementia (see Fig 4).

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Fig 4. Concept map of factors associated with self-reported all-cause dementia.

This figure shows various sociodemographic, health and social factors linked to dementia. Odds were lower for females (−66%), people who are obese (−40%), and those who are overweight (−38%). Odds were higher for individuals who are “young old” (+118%), have less than a high‑school education (+122%), have more than a bachelor’s degree (+121%), have one comorbidity (+116%), have two or more comorbidities (+250%), live in the West (+6%), or experience depression (+132), anxiety (+132), or rely on Medicaid or other public insurance (+113). Created in BioRender. Osei Duah, I. J. (2026) https://BioRender.com/qhuxlbg.

https://doi.org/10.1371/journal.page.0000025.g004

Globally, dementia has shown an increasing trend with notable geographical variation [2,36,37]. To address this rising burden, the 2024 Lancet Commission report highlighted several modifiable risk factors, including education, vascular health, sensory impairment, mental health, and social conditions, that contribute to dementia risk, and noted that efforts targeting these factors have helped reduce age‑specific incidence in several high‑income countries [31] In the U.S., however, the rapid expansion of the older adult population means that the absolute number of individuals living with dementia will continue to rise, underscoring the need to understand how comorbidity burden and psychosocial vulnerability shape cognitive health in later life [33,35,38,39]. Using nationally representative data, this study tested the hypothesis that middle-aged and older adults with a higher burden of sociodemographic, health-related, and psychosocial risk factors would have higher odds of self-reported all-cause dementia compared with those with fewer or no such risk factors.

Of note, the prevalence of self-reported dementia in our study population was below 2%, representing slightly more than 2,000 participants (see Table 1). This estimate differs from the 4.0% prevalence reported among NHIS 2022 participants aged ≥65 years [40], likely because our analysis included a broader age range (40 years and older), thereby capturing a larger proportion of younger adults with lower dementia prevalence. Compared with estimates from other regions, our observed prevalence was lower than that reported among African (2.4%) [41], European (5–10%) [42], and Eastern Asian populations (5–22%) [4]. Such variation likely reflects methodological and population-level differences across studies, including differences in age distributions, sampling frameworks, and underlying demographic characteristics [4,41,42]. In particular, our inclusion of middle-aged and younger older adults, rather than populations composed predominantly of very old adults, likely contributed to the lower observed prevalence, given the strong age-dependent increase in dementia risk [40,43]. Thus, inclusion of a broader age spectrum may provide insight into cognitive aging across midlife and older adulthood while simultaneously reducing overall prevalence estimates compared with studies restricted to adults aged ≥65 or ≥75 years (see Table 1). Furthermore, differences in diagnostic criteria, screening instruments, and case ascertainment approaches (clinical diagnosis versus screening-based identification) may contribute to variability in prevalence estimates through differential detection of mild or early-stage cases. Broader screening definitions may increase case identification, whereas stricter diagnostic thresholds or limited clinical confirmation may result in underestimation of dementia prevalence [4,41,42].

Unexpectedly, female sex was significantly associated with lower odds of self-reported all-cause dementia in this study (see Fig 3). The results should be interpreted cautiously and does not necessarily contradict previous evidence that demonstrate higher burden of specific dementia subtypes, particularly Alzheimer’s disease, among females [44]. The relationship between sex and dementia burden is complex, with prior studies reporting heterogeneous findings, including higher [44,45], lower [7,46], or no significant differences in dementia risk among females [45,47–50]. These inconsistencies may reflect differences in the dementia outcomes examined, as specific subtypes may have distinct biological mechanisms and sex-related risk profiles. Observed sex differences may also be influenced by biological factors, including apolipoprotein E genotype, sex hormone effects, and differences in brain aging trajectories [47,51–53], as well as social determinants such as educational attainment, socioeconomic status, healthcare access, and patterns of healthcare utilization [48,52,54–56].

Contrary to expectations [57,58], overweight and obesity were related with lower odds of self-reported all-cause dementia in this study (see Fig 3). This observation is consistent with patterns also reported in prior studies, including a meta-analysis by Danat et al. showing reduced dementia risk among overweight/obese older adults with shorter follow-up periods [48] and a Swedish longitudinal study with similar findings after nine years of follow up [59]. However, this relationship should be interpreted with caution, as this may reflect reverse causation and the heterogeneous nature of dementia subtypes rather than a true protective effect of higher BMI. In the preclinical phase of dementia, neurodegenerative changes can lead to appetite loss, metabolic alterations, and functional decline, resulting in unintentional weight loss; thus, lower BMI may reflect early disease processes rather than increased risk [60,61]. Other factors, including survival bias and selective attrition, may also contribute to this observed relationship, as individuals with obesity who survive into older age may represent a healthier and more resilient subgroup with distinct metabolic and vascular profiles [62–65]. Consistent with established evidence, aging remains a dominant risk factor, as reflected in the higher prevalence of self-reported all-cause dementia among younger older adults compared with middle-aged individuals, aligning with well-documented age-related increases in cognitive vulnerability [62–65].

Naturally, aging is accompanied by progressive structural and functional brain changes, including synaptic loss, reduced neuroplasticity, vascular stiffening, chronic low-grade neuroinflammation, and impaired clearance of neurotoxic proteins, all of which collectively increase susceptibility to cognitive decline and dementia [66,67]. Consistent with well-established age-related neurobiological changes, our findings showed that individuals in the young-old age group, compared with middle-aged adults, had significantly higher odds of reporting a dementia diagnosis. This relationship highlights the potential emergence of increased cognitive vulnerability during early older adulthood, when age-related reductions in brain reserve and resilience may contribute to greater susceptibility to cognitive impairment. (see Fig 3). This pattern aligns with epidemiological evidence demonstrating a steep age-gradient in dementia incidence, where risk increases disproportionately with advancing age due to cumulative biological wear and reduced compensatory capacity of neural networks [62–65]. Collectively, these results reinforce aging as the strongest non-modifiable risk factor for dementia and highlight the transition from midlife to older adulthood as a critical period to identify and address factors related with cognitive vulnerability.

Lower educational attainment was significantly related to a higher likelihood of self-reported all-cause dementia in this study (see Fig 3). This finding is consistent with the Lancet Commission report, which identifies low education as a major modifiable risk factor for dementia [68]. Similarly, evidence from the Japan Gerontological Evaluation Study, which followed older adults over six years, showed that communities with lower educational attainment experienced a higher risk of dementia, even after accounting for individual years of schooling [69]. A systematic review further reported that lower education was related to an increased risk of dementia in many, although not all studies, and that additional years of schooling did not consistently confer protection against dementia [70]. Likewise, McDowell and colleagues, using data from the Canadian Study of Health and Aging, reported a strong graded relationship between education and dementia risk, with individuals who had fewer than six years of schooling exhibiting more than twice the risk of dementia compared with those who had thirteen or more years of education; this relationship was even stronger among survivors [71]. Several mechanisms may explain this relationship. For instance, lower educational attainment may contribute to reduced cognitive reserve and fewer opportunities for lifelong cognitive stimulation [68,69]. It may also reflect limited cognitive development in early life [72], reduced access to cognitively enriching environments, and greater exposure to socioeconomic disadvantage across the life course [73]. These factors may collectively increase vulnerability to neurodegeneration and dementia in later life [72]. Taken together, these findings support a life-course perspective, suggesting that educational quality, cognitive enrichment, and sustained intellectual engagement may be more important determinants of dementia risk than years of schooling alone [70].

Residence in the western region of the U.S. was related to a higher likelihood of self-reported all-cause dementia (see Fig 3). However, this relationship should be interpreted with caution, as it may reflect underlying contextual and demographic factors rather than a direct geographic effect. Several mechanisms may contribute to this finding, including regional differences in healthcare access and utilization, availability of dementia-related services, migration patterns, and variation in diagnostic practices. In addition, the relatively large populations of older adults in some western states, geographic dispersion that may limit access to primary healthcare services, and socioeconomic disparities may contribute to differences in the prevalence of dementia [74]. Regional variation in educational opportunities, occupational characteristics, and exposure to environmental risk factors such as air pollution may also influence dementia risk across populations. [75]. Consequently, the observed regional relationship is likely multifactorial and may reflect broader social, environmental, and healthcare-related determinants of cognitive functioning rather than a solitary effect of geographic location.

The study found that living with one and/or two or more comorbid conditions was related to a higher likelihood of self-reported all-cause dementia compared with having no chronic health conditions (see Fig 3). This finding is consistent with evidence from Taiwan’s National Health Insurance Research Database, which examined the combined effects of type 2 diabetes and subsequent hypertension. Individuals with type 2 diabetes who later developed hypertension had a 51% higher risk of all‑cause dementia and a 130% higher risk of vascular dementia than those who did not develop hypertension [76]. Similarly, a population‑based prospective cohort study using UK Biobank data reported that multimorbidity defined using an extended list of chronic conditions that included several conditions assessed in the present study, was related to a nearly two-thirds higher risk of having dementia [77]. Furthermore, using data from the French National Health Data System (Système National des Données de Santé, SNDS) Carcaillon-Bentata et al. found that cardiometabolic comorbidities including diabetes and cardiovascular diseases were strongly associated young‑onset dementia [78]. One plausible explanation to these patterns of observation is that the cumulative physiological burden imposed by multiple chronic conditions may accelerate neurodegenerative processes, thereby heightening vulnerability to dementia [79,80].

Anxiety was a significant predictor of a higher likelihood of self-reported all-cause dementia in this study (see Fig 3). The results corroborate with evidence from the Caerphilly Prospective Study, which reported that higher anxiety levels were related to approximately one-third increase in dementia risk among participants [81]. Similarly, a systematic review and meta-analysis by Becker and colleagues found that anxiety was related to a 50% higher risk of Alzheimer’s disease and nearly a twofold increase in the risk of vascular dementia [82]. Another meta-analysis by Gulpers and coworkers further showed that, compared with individuals without anxiety, those with anxiety had increased incidence of cognitive impairment and dementia by 77% and 57%, respectively [83]. Likewise, Santabárbara et al. reported that anxiety was associated with a 29% increased risk of dementia [84]. The Hunter community study further demonstrated that both chronic anxiety and incident (new-onset) anxiety at follow-up were associated with an approximately three times higher risk of all-cause dementia [85]. Collectively, these findings suggest a consistent relationship between anxiety and later cognitive decline. Of note, this relationship may be best understood within a two-hit hypothesis framework, which proposes that early-life or midlife vulnerability factors constitute a first hit, while subsequent neurobiological or psychosocial stressors act as a second hit that accelerates neurodegenerative processes leading to dementia [86]. Within this framework, anxiety may contribute to the initial vulnerability through chronic stress-related neuroendocrine dysregulation [87,88] and vascular dysfunction [89]. At the same time, anxiety may emerge as a consequence of neuropathological changes, which represents a prodromal neuropsychiatric manifestations of dementia [90]. Together, this result suggests a dynamic and bidirectional relationship in which anxiety functions both as a potential risk factor for dementia and as an early clinical manifestation of ongoing cognitive decline.

In this study, having depression was related to a significantly higher likelihood of self-reported all-cause dementia (see Fig 3). This finding aligns with evidence from a large prospective cohort study by Snowden et al. [91], which reported that individuals with mild cognitive impairment or dementia were more than twice as likely to experience depression compared with those with normal cognition [91]. Gallagher and colleagues similarly found that active depression within the preceding two years was related to an increased the risk of Alzheimer-related dementia by nearly half [92]. Further, results from a longitudinal study by Van der Mussele and coworkers demonstrated that severe depressive symptoms in individuals with mild cognitive impairment were strongly related to progression to Alzheimer’s disease [93]. Evidence from a large Danish cohort further reinforces this pattern, demonstrating that depression in middle or late life was associated with more than a twofold increase in subsequent dementia risk [94]. In addition, the Lancet commission has also identified depression as a major risk factor and determinant for developing dementia [31]. However, the temporal relationship is complex, as depression may also represent an early manifestation of neurodegenerative pathology [95]. The shared neuropathobiological mechanisms such as chronic stress activation, neuroinflammation, reduced neuroplasticity, and vascular dysfunction may underlie both depressive symptoms and cognitive decline, suggesting overlapping and potentially bidirectional pathways [96,97].

Enrollment in Medicaid insurance was related to a higher likelihood of self-reported all-cause dementia in this study (see Fig 3). However, this relationship likely reflects characteristics of the populations served by Medicaid rather than a causal effect of insurance coverage. Medicaid disproportionately covers older adults, individuals with disabilities [98], and those requiring long-term care, populations that are also at elevated risk for dementia. Furthermore, the substantial costs associated with dementia-related care often lead to Medicaid eligibility, introducing the possibility of reverse causation [99,100]. Increased health care utilization and greater contact with healthcare and institutional settings among Medicaid beneficiaries may also facilitate earlier recognition and diagnosis of dementia [101–103]. Collectively, the higher odds of dementia among Medicaid enrollees as observed in this study may be best explained by the underlying socioeconomic, health, and care-related factors rather than Medicaid itself.

The strength of this study lies in its use of nationally representative NHIS data across six survey waves to characterize the recent burden of self-reported dementia and associated risk factors among U.S. adults aged 40 years and older. By leveraging a large population-based surveillance dataset, this study provides important insights into the distribution of dementia burden and its relationship with sociodemographic, health, and behavioral factors across the aging trajectory. The use of self-reported dementia status offers a pragmatic approach for population-level monitoring, as it captures dementia diagnoses identified within routine healthcare settings and enables evaluation of dementia burden in settings where comprehensive clinical assessments, biomarker evaluation, or neuropsychological testing are not feasible. However, some limitations should be considered when interpreting these findings. First, dementia status was determined using a single NHIS self-report item that does not distinguish among specific dementia etiologies, including Alzheimer’s disease, vascular dementia, Lewy body dementia, and frontotemporal dementia. Although these disorders share common clinical features, they differ in underlying neuropathology, disease progression, and risk factor profiles [1,104]. Consequently, the observed associations may reflect relationships with overall dementia burden rather than disease-specific pathways, and risk factors that are particularly relevant to individual dementia subtypes may not be adequately captured. This limitation reflects the structure of the NHIS instrument rather than an analytic decision. Even if subtype-specific data had been available, the relatively small number of participants with dementia may have limited statistical power for subtype-specific analyses and constrained the ability to examine etiologically distinct dementia conditions in greater detail.

Second, reliance on self-reported dementia diagnoses may introduce recall bias, misclassification, and underdiagnosis, particularly among individuals with limited healthcare access, early cognitive impairment, or undiagnosed disease. Although proxy respondents are included in NHIS to improve representation of individuals unable to respond independently, the household survey design may still result in underrepresentation of individuals with more advanced dementia who are institutionalized, medically complex, or less able to participate. As a result, the estimated prevalence and associated risk patterns may underestimate the burden among individuals with severe cognitive impairment. In addition, because NHIS captures cross-sectional observations within each survey wave, causal relationships between identified risk factors and dementia cannot be established, and temporal changes in associations should be interpreted cautiously. Despite these limitations, the inclusion of six NHIS waves provides repeated nationally representative observations over time, strengthening the reliability of prevalence estimates and enabling a comprehensive assessment of dementia-related patterns and associated risk factors at the population level. These findings contribute to ongoing efforts to understand the evolving burden of dementia in the United States and highlight the need for future studies incorporating clinical phenotyping, biomarkers, and longitudinal follow-up to better characterize subtype-specific mechanisms and trajectories of cognitive decline.

Conclusions

This study provides nationally representative evidence that self-reported all-cause dementia affects approximately one in 100 adults in the U.S., with prevalence increasing substantially with advancing age and greater comorbidity burden. Female sex and higher BMI (overweight and obesity) were related with lower odds of reported dementia, whereas young-old age, lower educational attainment, residence in the Western region, multimorbidity, depression, anxiety, and Medicaid insurance coverage were related with higher odds of dementia. These findings highlight the multifactorial nature of dementia vulnerability and identify potential targets for prevention, risk reduction, and improved healthcare delivery. Strategies to reduce dementia burden should emphasize comprehensive management of chronic conditions through integrated primary care, early identification and control of cardiometabolic risk factors, and expansion of mental health services that incorporate routine screening and timely treatment of depression and anxiety. In addition, promoting educational opportunities and lifelong cognitive engagement may contribute to cognitive reserve and support healthy aging across the life course. The increased burden observed among young-old adults further underscores the importance of early risk assessment and prevention efforts before substantial cognitive decline occurs. Although higher BMI was related with lower odds of dementia in this analysis, this finding should be interpreted cautiously, as it may reflect reverse causation, including weight loss related with preclinical dementia, rather than a protective effect of higher BMI. Taken together, reducing dementia burden will require coordinated, life-course approaches that integrate chronic disease management, mental health support, cognitive health promotion, and equitable access to preventive and diagnostic services.

Acknowledgments

The authors acknowledge the support of Dr. Reginald Gyamfi Acquah (Department of Optometry and Visual Sciences) and Ms. Bernice Lebene Tettey (Department of Chemistry), both of the College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, for their technical assistance and for proofreading the manuscript.

Disclaimer

The views expressed in this article are those of the authors and do not necessarily reflect the policies of the NHIS.

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