Abstract

Objectives The rapid aging of the U.S. population has raised concerns about age-related cognitive decline and Alzheimer’s disease. As of 2024, 18% of Americans are ≥65 years—up from 12.4% in 2004—contributing to a projected 7.2 million cases of Alzheimer’s disease among older adults in 2025. Diet is a key modifiable factor for cognitive decline. Therefore, we aimed to characterize diet quality and nutrient intake and to examine the associations between specific dietary components and cognitive performance in older adults in the American Midwest.

Design The study was designed as a cross-sectional observational study.

Setting Community-based recruitment in Brookings, South Dakota, and surrounding areas

Participants A final analytical sample of 72 community-dwelling adults aged 65 years and older

Measurements Cognitive performance was assessed using subtests from the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery, evaluating episodic memory (Word List Memory/Recall/Recognition), visuospatial skills (Constructional Praxis), and executive function (Verbal Fluency). A composite cognitive score was calculated from memory and visuospatial subtests. Habitual dietary intake was evaluated using structured 24-hour recalls to calculate nutrient intake and the Healthy Eating Index score, supplemented by the Short HEI questionnaire. Demographics, health history, depressive symptoms (Patient Health Questionnaire-9), and sleep quality (Pittsburgh Sleep Quality Index) were also collected.

Results Participants demonstrated suboptimal diet quality (mean HEI score 54.4 ± 9.4; recommended >80), with only 9.7% meeting fiber recommendations, 11% meeting calcium or vitamin A recommendations, and 1.4% meeting vitamin D requirements. In bivariate comparisons, higher cognitive performance was observed in younger participants (75.5 vs. 79.5 years; p<0.01) and females (78% vs. 50%; p=0.024). Regression models identified significant positive associations between cognitive scores and intakes of dietary fiber (p=0.007), unsaturated fats (mono- and polyunsaturated; p=0.012–0.033), protein (p=0.018), carotenoids (α-carotene, p=0.001; β-carotene, p=0.026; lutein+zeaxanthin, p=0.016), vitamins A (p=0.044) and E (p=0.034), and minerals including magnesium (p=0.006), potassium (p=0.004), copper (p=0.008), zinc (p=0.024), and calcium (p=0.035). Refined grain intake was inversely associated with cognition (p=0.011).

Conclusion In this population, dietary components like fiber and micronutrients were positively associated with better cognitive function, and the overall nutrient intake shortfalls observed highlight the need for targeted dietary interventions to support healthy brain aging.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This research received no external funding. This work was supported by the South Dakota State University College of Education and Human Sciences Pilot Study Funding Program

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was done in accordance with Declaration of Helsinki and was approved by the Institutional Review Board (IRB) at South Dakota State University (IRB-2024-56).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Data Availability

All data produced in the present study are available upon reasonable request to the authors

AbbreviationsADAlzheimer’s DiseaseAMDRAcceptable Macronutrient Distribution RangeCERADConsortium to Establish a Registry for Alzheimer’s DiseaseHCPHigh Cognitive PerformanceIRBInstitutional Review BoardLCPLow Cognitive PerformancePHQ-9Patient Health Questionnaire-9PSQIPittsburgh Sleep Quality IndexRDARecommended Dietary AllowancesHEIShort Healthy Eating Index