Exploring the effect of lifestyle factors on cognitive decline among Blacks/African population in the USA: Results from the national alzheimer's coordinating center (NACC) dataset

Introduction

Dementia and cognitive decline have become major global public health issues, especially among older populations. According to the World Health Organisation (WHO), there are already over 55 million dementia sufferers worldwide; as the population ages and life expectancy rises, this figure is predicted to triple by 2050 (WHO, 2021). Although dementia is a condition that affects people of all races and ethnicities, socioeconomic, environmental, and genetic factors cause considerable differences in its prevalence, progression, and effect across different groups.¹

Black/African communities endure a disproportionate burden of cognitive decline and dementia. Studies reveal that individuals from these communities are at a higher risk compared to their White counterparts, even after adjusting for socioeconomic level and education.² There are several reasons for this discrepancy, such as inadequate representation in clinical research, health disparities, and systemic injustices.³ Targeted research and interventions are essential since these risks are further increased by the combination of systemic racism, historical injustices, and inadequate accessibility to healthcare. The higher risk shown in Black/African communities about cognitive health cannot be completely explained by genetic predisposition alone. Rather, elements that can be changed, such as lifestyle choices and psychological stressors, are crucial.

Research suggests that addressing these modifiable factors can enhance outcomes and drastically change the course of cognitive decline.⁴ It is commonly known that some lifestyle choices, like smoking, drinking alcohol, and being obese, can lead to cognitive deterioration. For example, there is a complicated link between body mass index (BMI) and cognition. Low BMI in later life can potentially be a sign of frailty and imminent cognitive impairment, even while midlife obesity is linked to an increased risk of dementia.⁴ The study's dataset highlights the importance of BMI as a predictor, as participant levels vary greatly, indicating a range of health profiles.

Alcohol use and smoking increase these hazards much more. According to,⁵ smoking causes oxidative stress and vascular damage, both of which are detrimental to brain function. Similar to extreme alcohol use, moderate alcohol usage has been disputed for its possible preventive benefits, while excessive use is associated with neuronal damage and decreased cognitive reserve.⁶ Cultural beliefs and the availability of smoking cessation programs may have an impact on these behaviours and the risks they pose among Black and African Americans.

Physical activity is protective against cognitive deterioration and is frequently inversely correlated with BMI. Frequent exercise enhances cognitive performance, encourages neurogenesis, and improves cardiovascular health.⁷ However, obstacles like lack of recreational facilities, hazardous neighbourhoods, and socioeconomic limitations frequently restrict physical activity in Black and African communities, indicating a need for public health intervention.

Cognitive trajectories are greatly impacted by psychosocial factors, such as anxiety, depression, and ongoing stress. Both a risk factor and a prodromal symptom of dementia have been found for depression, which is frequently underdiagnosed in Black and African American communities.⁸ Nuanced analyses of this association are made possible by the dataset's inclusion of factors like the Geriatric Depression Scale (GDS).

Cognitive decline is further aggravated by chronic stress and trauma, which are frequently caused by systemic racism and socioeconomic injustices. According to the allostatic load theory, extended exposure to stress hormones causes the body, particularly the brain, to deteriorate.⁹ This is especially important for Black and African communities, who often face stresses such as insufficient social support, economic instability, and prejudice.

An additional important psychosocial component is social connectivity, or the absence of it. Loneliness and isolation are becoming more widely acknowledged as risk factors for cognitive decline.¹⁰ On the other hand, robust social networks can enhance cognitive resilience and mitigate the impact of stress. Designing treatments that take advantage of these protective features requires an understanding of the social dynamics inside Black/African communities.

One of the best indicators of cognitive outcomes is education; higher levels of education are linked to increased cognitive reserve and resistance to dementia pathology (Stern, 2012). For many Black and African Americans, however, especially older folks who grew up during times of segregation and limited access to high-quality education, historical and institutional restrictions have led to lower levels of educational achievement. The relationship between education and socioeconomic status (SES) affects stress exposure, healthcare availability, and lifestyle choices. The risk of dementia is increased by obesity, smoking, and untreated hypertension, all of which are frequently associated with lower socioeconomic status (SES).¹¹ In Black and African communities, these risks are further exacerbated by healthcare inequities, such as delayed diagnoses and inadequate treatment.

Black/African communities are disproportionately affected by hypertension, a modifiable risk factor that frequently manifests at younger ages and with greater severity than in other groups.^12,22 Prolonged hypertension raises the risk of vascular dementia, destroys blood vessels, and lowers brain perfusion. With implications for both preventative and treatment measures, the dataset emphasises hypertension and its management as crucial variables.^4,24 The dataset's records on the usage of lipid-lowering and hypertensive drugs offer more information about treatment adherence and how it affects cognitive outcomes. The underutilisation of lifestyle changes despite the effectiveness of pharmaceutical therapies suggests the necessity for culturally specific education and support initiatives. Lifestyle, psychological, and demographic factors interact in a complicated and multidimensional way.^13,23

There are important public health ramifications to comprehending the modifiable factors impacting cognitive decline in Black and African communities. The burden of dementia could be significantly decreased by interventions that address social isolation, depression, smoking, and obesity. This study therefore is aimed at exploring the effect of Lifestyle Factors on Cognitive Decline among the Black/African population in the USA using the National Alzheimer's Coordinating Center (NACC) dataset

Methods

This study employed a cross-sectional analysis using data from the National Alzheimer's Coordinating Center (NACC) Uniform Data Set (UDS) to examine the association between demographic, lifestyle, and medical factors with cognitive decline among Black/African American adults. The dataset provides standardized clinical, neuropsychological, and lifestyle information collected from multiple Alzheimer’s Disease Research Centers (ADRCs) across the United States.¹⁷ The assessment tool used in this study is derived from publicly available datasets provided by the National Alzheimer’s Coordinating Center (NACC) and is not a proprietary research instrument. Therefore, no copyright license is required for its use.

Participants were included if they self-identified as Black/African American, were at least 50 years old, and had available cognitive assessment scores (Mini-Mental State Examination (MMSE) and Clinical Dementia Rating (CDR) sum of boxes), as well as documented lifestyle and medical history. Cases with excessive missing data (>20% missing values across key variables) were excluded. Variables with ≤10% missingness underwent multiple imputations using the Multivariate Imputation by Chained Equations (MICE) method to preserve statistical power. Continuous variables such as age, BMI, systolic blood pressure, and depression scores were standardized (mean = 0, SD = 1), while education level was categorized into five levels: below high school, high school, bachelor’s, master’s, and doctorate. Smoking and alcohol use were treated as binary variables.

To ensure transparency and reproducibility, we followed the EQUATOR Network guidelines for reporting observational studies. Data processing and statistical analysis were conducted using RStudio (version 2023.12.0+368) with relevant statistical packages, including tidyverse for data manipulation and visualization, mice for multiple imputation, lme4 for mixed-effects modeling, and car for regression diagnostics. Descriptive statistics were used to summarize demographic, health, and cognitive characteristics, while Pearson correlation coefficients were computed to assess relationships among key variables.

Multivariable logistic regression was used to examine predictors of dementia diagnosis (CDR score ≥1.0), adjusting for age, sex, education, BMI, smoking, alcohol use, hypertension, and depression score. To evaluate cognitive trajectories, a linear mixed-effects model (LMM) was employed to assess MMSE scores over time, incorporating a random intercept for individuals to account for within-subject variability. Interaction effects (e.g., age × BMI, hypertension × depression) were tested and retained if statistically significant (p < 0.05).

Model evaluation included multicollinearity assessment using the Variance Inflation Factor (VIF), with a threshold of VIF < 5 indicating no problematic collinearity. Model fit was assessed using the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). Sensitivity analyses were conducted, including complete-case analysis and alternative methods for handling missing data, to ensure the robustness of the findings.

By leveraging a large, well-characterized dataset and advanced statistical modelling, this study provides a rigorous examination of cognitive decline and its predictors in the Black/African American population.

Results

The study included 24,476 participants, most of whom were female (74.1%). The average age was around 74.5 years, with a wide range spanning from 28 to 108 years. Education levels varied significantly, with nearly half of the participants (46.84%) having completed high school, while 18.74% had a bachelor's degree, 18.52% had a master’s, and only 5.14% had a doctorate as included in Table 1. This suggests that most participants had some level of formal education, which could influence cognitive outcomes.

Table 1 presents the socio-demographic characteristics of the study participants, including age, education level, BMI, and hypertension prevalence.

The average BMI of 29.46 kg/m² [ Table 1] indicates that many participants were overweight or obese, a known risk factor for various chronic conditions, including cognitive decline. Additionally, blood pressure levels were relatively high, with an average systolic pressure of 137.13 mmHg, further emphasizing the role of vascular health in cognitive function. The average Mini-Mental State Examination (MMSE) score was 25.10, indicating mild cognitive impairment in many individuals, while the Geriatric Depression Scale (GDS) score of 1.77 suggests mild depressive symptoms among the population.

Table 2 shows that Smoking prevalence was relatively low, with only 8% of participants reporting smoking, but alcohol use was common, with nearly half (48.77%) consuming alcohol. A strikingly high percentage (77.1%) had hypertension, reinforcing the significant burden of cardiovascular risk factors in this population. Despite this, only 8.02% of participants were taking hypertensive medications, suggesting possible gaps in treatment adherence or access to care. The use of lipid-lowering medications was more prevalent (45.23%), indicating awareness and treatment of cardiovascular risk factors. Mental health conditions such as anxiety and PTSD were less common, affecting 10.34% and 4.5% of participants, respectively. However, given that mental health issues are often underdiagnosed in Black/African communities, the actual prevalence could be higher.

The correlation matrix in Figure 1 reveals significant associations between cognitive function and key predictors. Figure 1 was generated from our analysis using the study dataset. No external permissions were required for its use. Age showed a strong negative correlation with MMSE scores (r ≈ -0.50) and a positive correlation with CDR scores (r ≈ 0.45), confirming that cognitive decline worsens with ageing. Education was positively correlated with MMSE (r ≈ 0.40, p < 0.001) and negatively correlated with CDR (r ≈ -0.35, p < 0.001), reinforcing its protective effect against dementia. Depression (GDS score) had a negative correlation with MMSE (r ≈ -0.38, p < 0.001) and a positive correlation with CDR (r ≈ 0.42, p < 0.001), emphasizing the strong link between mental health and cognitive decline. Systolic blood pressure (BPSYS) showed a weak negative correlation with MMSE (r ≈ -0.15, p < 0.001) and a slight positive correlation with CDR (r ≈ 0.10, p = 0.0008), highlighting the impact of vascular health on cognition. BMI had a slight positive correlation with MMSE (r ≈ 0.12, p < 0.001) but a negative correlation with CDR (r ≈ -0.10, p < 0.001), suggesting a complex relationship where midlife obesity may increase dementia risk, while low BMI in later life may indicate frailty and cognitive impairment. These findings reinforce the need for targeted interventions in mental health, vascular health, and education to mitigate cognitive decline and dementia risk in Black/African populations.

Figure 1. Correlation Matrix to assess correlations between continuous predictors and cognitive outcomes.

BMI: Body Mass Index, BPSYS: Systolic blood pressure, MMSE: Mini-Mental State Examination, GDS: Geriatric Depression Scale, CDR: Clinical Dementia Rating score.

The results from the regression analysis in Table 3 provide valuable insights into the predictors of cognitive function and dementia risk among Black/African populations.

Older age was strongly associated with worse cognitive performance, as indicated by a -0.09 decrease in MMSE score per additional year of age (95% CI: -0.10 to -0.08, p < 0.001). Similarly, age was positively associated with higher dementia severity, showing a 0.05 increase in CDR score per year (95% CI: 0.04 to 0.05, p < 0.001). These findings confirm that cognitive decline progresses with ageing, reinforcing the need for early interventions in ageing populations.

Higher education was significantly associated with better cognitive function. Each additional level of education increased the MMSE score by 0.42 points (95% CI: 0.40 to 0.45, p < 0.001) and decreased the CDR score by 0.14 points (95% CI: -0.15 to -0.12, p < 0.001). These results support the cognitive reserve hypothesis, which suggests that education provides resilience against neurodegeneration and delays cognitive impairment.

BMI showed a mixed effect on cognition. A higher BMI was associated with better cognitive scores, as indicated by a 0.13-point increase in MMSE per BMI unit (95% CI: 0.11 to 0.14, p < 0.001). However, it was also linked to higher dementia severity, with a -0.08 decrease in CDR score per BMI unit (95% CI: -0.09 to -0.07, p < 0.001). This suggests that while obesity in midlife may be a risk factor for dementia, lower BMI in later life may reflect frailty, which is also associated with cognitive decline.

Depression was significantly associated with worse cognitive outcomes. A one-point increase in GDS score was linked to a 0.27-point decline in MMSE score (95% CI: -0.31 to -0.23, p < 0.001) and a 0.24-point increase in dementia severity (CDR score) (95% CI: 0.22 to 0.26, p < 0.001). These findings emphasize the strong link between mental health and cognitive decline, suggesting that depression could be both a risk factor and an early sign of dementia.

Higher systolic blood pressure was significantly correlated with worse cognitive function, with each 1 mmHg increase in blood pressure reducing MMSE scores by 0.01 points (95% CI: -0.02 to -0.01, p < 0.001). Additionally, an increase in blood pressure slightly increased dementia severity, with a 0.00 to 0.01 rise in CDR score (p = 0.0008). These findings reinforce the link between vascular health and cognition, indicating that proper blood pressure management could help reduce cognitive decline.

Discussion

This study examined how demographic, and lifestyle factors influence cognitive decline and dementia risk among Black/African populations. Using the NACC dataset, statistical analyses revealed significant associations between cognitive outcomes (MMSE and CDR Sum scores) and predictors such as age, education, BMI, hypertension, and mental health indicators.

Older age was associated with lower MMSE scores and higher CDR Sum scores, confirming age as a strong risk factor for cognitive impairment. Education level varied significantly, with most participants having at least a high school diploma where a one-year increase in education was associated with a 0.42-point increase in MMSE scores and a 0.14-point reduction in CDR Sum scores indicating that higher education significantly delays cognitive decline. These findings align with the cognitive reserve hypothesis, which suggests that higher educational attainment provides resilience against neurodegeneration.^13,21

The mean BMI of participants was 29.46 kg/m², indicating a high prevalence of overweight and obesity. Higher BMI was linked to lower MMSE scores) and higher CDR Sum scores, suggesting an increased dementia risk. However, subgroup analyses revealed a non-linear relationship where high BMI in midlife was harmful, but low BMI in late life was associated with cognitive decline, possibly due to frailty.^14,20

Those with hypertension had lower MMSE scores and higher dementia risk and Blood pressure (systolic) had a weak but significant relationship with cognitive outcomes where Higher systolic BP was associated with lower MMSE scores and Higher systolic BP correlated with a slight increase in dementia risk. These findings reinforce the link between vascular health and cognitive function, suggesting that early blood pressure control may reduce dementia risk.^12,15,19

The high prevalence of hypertension (77.1%) among participants suggests that vascular health is a critical factor in cognitive ageing. Regression analysis indicated that each 10 mmHg increase in systolic blood pressure (BPSYS) was associated with a 0.11-point decrease in MMSE scores and a slight but significant increase in CDR Sum scores. These findings align with prior studies linking hypertension to vascular dementia and Alzheimer's disease.^16,18 Additionally, 8.02% of participants were on hypertensive medication, and while medication use was not directly correlated with improved cognitive outcomes, controlled hypertension has been shown to slow cognitive decline in longitudinal studies. This suggests the need for a combination of pharmacological and lifestyle interventions to mitigate the cognitive risks of hypertension.

Participants with higher depression scores (NACCGDS) had lower cognitive scores, reinforcing the bidirectional relationship between depression and dementia.^16,17 A one-point increase in GDS score was associated with a 0.27-point decrease in MMSE scores. Higher depression scores were linked to an increase in dementia risk. Anxiety and PTSD, while less prevalent, showed similar patterns, indicating that chronic stress and trauma contribute to cognitive deterioration. The allostatic load theory suggests that prolonged exposure to stress hormones accelerates brain ageing.^1,2,17 These findings highlight the importance of integrating mental health screening into dementia prevention strategies, particularly in Black/African communities where mental health care may be underutilized.

Women had slightly higher MMSE scores (Mean = 25.4) compared to men (Mean = 24.7, despite similar hypertension and BMI distributions. However, women exhibited higher depression and anxiety scores, potentially increasing their vulnerability to dementia in later life. These findings show the need for gender-specific interventions, particularly mental health support for women and targeted vascular risk reduction for men.

Conclusion

This study provides crucial insights into the cognitive health of Black/African populations, emphasizing the interplay of demographic, lifestyle, and psychosocial factors in dementia risk.

Higher education levels were strongly linked to better cognitive outcomes, reinforcing the importance of lifelong learning and cognitive engagement while Higher BMI and elevated blood pressure were associated with lower cognitive performance, highlighting the need for cardiovascular risk management.

Mental health factors significantly impacted cognitive function, stressing the importance of integrating mental health care into dementia prevention, Women had better cognitive scores but higher mental health risks, while individuals with lower education levels faced greater cognitive decline.

Ethical considerations

This study utilized secondary data from the National Alzheimer’s Coordinating Center (NACC). Informed written consent was obtained by the original investigators from all participants prior to data collection. The dataset was fully anonymized to protect participant confidentiality, and our study adhered to all ethical guidelines outlined in the Declaration of Helsinki.

Consent for publication

Not applicable.

Authors’ contributions

Dare Imolore Ezekiel and Apochi Obed Okwol conceptualised the study, downloaded the dataset, analysed the data discussed the results and wrote the introduction, Egwu Matthew and Isaac Isiko reviewed the first draft of the manuscript and Isaac Isiko formatted and compiled the final draft of the manuscript. All the authors reviewed and approved the final draft of the manuscript.