What older adults eat may shape dementia risk

by · News-Medical

A nationally representative US study links higher intake of ultraprocessed foods to greater risk of dementia and cognitive impairment, while minimally processed foods may help support healthier brain aging.

Study: Ultraprocessed Foods and the Risk of Cognitive Impairment and Dementia in Older US Adults: 2013–2020 Health and Retirement Study. Image Credit: Lemberg Vector studio / Shutterstock

The study’s analyses assessed diet at baseline. They tracked cognitive status over follow-up, revealing that the highest quintile of UPF intake in the sample cohort was associated with a 58% higher risk of dementia compared to the lowest quintile. However, the linear trend across quintiles was not statistically significant. Conversely, minimally processed foods showed protective trends. While these findings suggest that reducing processed foods may support cognitive health, several methodological caveats warrant a cautious interpretation.

Ultraprocessed Foods and Brain Health

Ultraprocessed foods (UPFs) represent a dominant share of modern diets, particularly in Western and increasingly industrialized food systems. However, recent evidence indicates that these industrially engineered formulations contain numerous chemical additives, stabilizers, and preservatives to aid processing and extend shelf life. Some of these additives and processing-related exposures have been proposed as potential contributors to long-term physiological effects, although direct human evidence remains limited.

Public health reports already indicate that in the United States (US), the convenience of easy-to-consume UPFs has led these foods to now account for more than half of daily energy intake among US adults. Although prior prospective studies have linked UPF diets to metabolic disorders, type 2 diabetes (T2D), and cardiovascular diseases (CVDs), evidence regarding their impact on the aging brain remains mixed.

Specifically, while some previous cohorts have demonstrated accelerated cognitive decline, others report no significant associations with mild cognitive impairment, thereby hampering public health recommendations and clinical practice. Clarifying these dietary links using representative cohorts is essential to guide clinical counseling and policy decisions.

HRS Cognitive Aging Study Design

The present longitudinal study aimed to address this knowledge gap and inform future US adult dietary guidelines by leveraging data from the long-term Health and Retirement Study (HRS; 2013–2020) and the HRS’s Health Care and Nutrition Study (2013 dataset).

The study’s sample dataset comprised 5,370 participants aged 50 years and older with UPF intake data, no prior history of Alzheimer’s disease, dementia, or memory problems at baseline, and no cognitive impairment during the first 2 years of follow-up. To minimize the potential for reverse-causal interpretation, individuals who developed cognitive issues within the first 2 years of follow-up were excluded from the subsequent analysis.

In addition to participants' sociodemographic and medical histories, the study quantified dietary exposure using a validated semistructured food frequency questionnaire (FFQ) based on the Harvard FFQ, with items categorized according to the NOVA food classification system.

Participants’ energy-adjusted dietary intake was computed (in grams) to better represent low-calorie, high-weight items, which have traditionally been under- or poorly represented in similar datasets. In this cohort, UPFs accounted for 21.5% of total food intake by grams and 42.4% of total energy intake, while minimally processed foods accounted for 71.8% of total food intake by grams and 43.1% of total energy intake. Finally, participants’ cognitive status was assessed biennially using the Langa-Weir classification, which scores word recall and attention tasks on a standardized and previously validated 27-point scale.

Statistical analyses leveraged Cox regression models that were controlled for participants' sociodemographic and medical status, particularly age, gender, race, education, wealth, physical activity, smoking, and chronic health conditions.

UPF Intake and Dementia Findings

During the 8.7 years of follow-up, study analyses documented 266 incident cases of dementia and 1,191 cases of cognitive impairment with no dementia (CIND). Crucially, the analyses revealed that high UPF intake was associated with higher cognitive risks, as illustrated by participants in the highest quintile of UPF consumption demonstrating a 58% higher risk of dementia (hazard ratio [HR] = 1.58) than their counterparts in the lowest quintile, although the dementia association was borderline and did not show a statistically significant linear trend across quintiles.

Similarly, the highest UPF intake cohort was found to experience 46% higher risk of CIND and a 47% higher risk of the composite CIND or dementia outcomes than those in the lowest quintile. However, when UPF intake was modeled as a percentage of total energy intake, the associations were attenuated, and the dementia association was no longer statistically significant.

Conversely, minimally processed foods correlated with lower risks. When analyzing food subcategories, processed meat was the only UPF subgroup independently associated with a higher risk.

While the mechanism underlying these observations remains unverified, the authors hypothesize that alterations in gut microbiota may affect brain-derived neurotrophic factor signaling cascades and neuroplasticity, thereby modulating cognitive performance, particularly in older adults. Other proposed pathways include oxidative stress, chronic inflammation, and potential effects of food additives, although much of this mechanistic evidence comes from animal or experimental studies rather than direct human confirmation.

Social isolation also appeared to be linked to stronger associations for CIND and the composite outcome, though the interaction was not statistically significant. The researchers did not assess dementia-specific effect modification by social isolation because of small case numbers in some strata.

Whole Foods and Public Health Guidance

The present study suggests the potential value of public health strategies that encourage older adults to choose whole, minimally processed foods over processed convenience foods. While the strength of its inferences was limited by its reliance on self-reported questionnaires rather than physiological or biochemical evaluations and by its use of survey-based cognitive scores rather than clinical diagnoses, its findings support cautious public health messaging that encourages lower UPF intake and greater consumption of minimally processed foods, while recognizing that overall diet quality, exposure misclassification, reverse causation, and residual confounding may partly explain the observed associations.

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