Globally, the aging population is increasing rapidly, leading to a dramatic rise in the prevalence of Alzheimer's disease and other types of dementia. Neurodegenerative disorders are characterized by pathological hallmarks such as β-amyloid (Aβ) plaque accumulation, tau protein aggregation, synaptic loss, and widespread neuroinflammation. These processes impair key cognitive domains including attention, memory, executive function, and orientation, hindering independent daily functioning.

Beyond cognitive decline, neurodegenerative diseases are associated with a marked deterioration in oromotor functions, such as chewing and swallowing. Mastication plays a critical role not only in digestion but also in neuro-sensory stimulation. Trigeminal nerve signaling activated by chewing enhances neurotransmitter release, boosts neurotrophic factor production (e.g., BDNF), and facilitates Aβ clearance, thereby supporting synaptic plasticity and reducing inflammation. Neuroimaging studies have shown that a higher number of functional occlusal pairs is associated with increased gray and white matter volume in regions affected early in Alzheimer's disease.

Systematic reviews have identified poor mastication and tooth loss as risk factors for cognitive decline and dementia. Mechanistically, loss of afferent input from the oral cavity-due to tooth loss, reduced chewing force, prosthetic use, or muscle atrophy-leads to reduced brain stimulation, diminished neurotrophic support, and impaired cerebral blood flow. Thus, geriatric-friendly chewing gum formulations with low elasticity and ease of chewing have been recommended.

Chewing gum is a promising vehicle for functional compounds due to its potential for transmucosal absorption and cognitive stimulation. Randomized controlled trials have shown that both active and inactive gums improve attention and reduce error rates in cognitive tasks, highlighting the beneficial effects of mastication.

Another emerging target for cognitive enhancement is the oral microbiota, a complex ecosystem of over 700 bacterial species. Dysbiosis in this ecosystem has been linked to neurological outcomes via inflammatory and neurotoxic pathways. Certain pathogens, such as Porphyromonas gingivalis, have been detected in the brains of Alzheimer's patients. Moreover, metagenomic studies have shown that reduced salivary microbial diversity correlates with poorer cognitive performance, even in young adults.

Elderberry (Sambucus nigra L.) is rich in anthocyanins (e.g., cyanidin-3-glucoside, cyanidin-3-sambubioside) with strong antioxidant and anti-inflammatory properties. Literature shows that polyphenols can be absorbed via buccal and sublingual mucosa, bypassing first-pass metabolism and providing faster systemic effects. However, the impact of anthocyanin-enriched chewing gum on oral microbiota and cognitive function has not yet been systematically investigated.

This study aims to develop and evaluate a geriatric-friendly functional chewing gum enriched with standardized elderberry anthocyanins. The intervention targets dual mechanisms-neurophysiological and microbial-to support cognitive health and balance oral microbiota in older adults.

This study is a double-blind, randomized controlled clinical trial designed to evaluate the impact of an elderberry-based functional chewing gum on cognitive function and oral microbiota in older adults.

The chewing gum intervention contains encapsulated anthocyanins derived from Sambucus nigra L., standardized for cyanidin-3-glucoside and cyanidin-3-sambubioside content, and formulated specifically for elderly individuals. The gum is designed to be soft-textured, low in elasticity, and easy to chew. It also allows transmucosal absorption through buccal and sublingual pathways, offering a rapid delivery system for polyphenols.

The study will enroll 34 participants aged 60 and above, with mild cognitive impairment (MoCA 20-25), divided equally into intervention and placebo groups. Participants will chew one gum twice daily for 6 weeks. During the intervention, participants will follow a berry-free diet to eliminate potential confounding sources of polyphenols.

Pre- and post-intervention assessments will include:

• Cognitive performance using MoCA and Stroop Color-Word Test (TBAG form)
• Salivary analysis for flow rate, pH, antioxidant capacity (FRAP), and total phenolic content (Folin-Ciocalteu)
• Microbiota profiling via 16S rRNA sequencing (in a subsample) and culturing of S. mutans and Lactobacillus spp.
• Compliance tracking via daily chewing logs and weekly monitoring

The primary hypothesis is that the anthocyanin-enriched gum will:

• Enhance cognitive performance,
• Improve oral microbial diversity,
• Reduce cariogenic bacteria (e.g., S. mutans),
• Increase salivary antioxidant capacity. Secondary goals include evaluating the gum's acceptability using a 9-point hedonic scale and assessing the stability of anthocyanin content over time.

Anthocyanin content and release will be validated by HPLC and pH-differential spectrophotometry, and stability will be tested over a 6-month period according to ICH guidelines. Statistical analysis will be performed using ANOVA, t-tests, and linear models adjusting for education and age.

This multidisciplinary study integrates dietary polyphenols, oral delivery systems, salivary biomarkers, microbiome science, and cognitive neuroscience in a novel, geriatric-focused intervention.

Inclusion Criteria:

• Individuals aged 60 and over
• Individuals with mildly reduced cognitive function using the MoCA test (MoCA score: 20-25)
• Those with stable systemic diseases (e.g. HT, controlled DM)
• Those with adequate dental health (≥20 natural teeth or no chewing problems with functional prosthesis)
• Non-smokers and those who use regular medication and do not use antibiotics or antiseptic mouthwashes that could seriously affect the oral microbiota
• Individuals who are willing to participate in the study and can give written consent

Exclusion Criteria:

• Moderate to severe dementia (MoCA < 20)
• Presence of active infection or systemic inflammatory disease
• Temporomandibular joint disorders affecting gum chewing function
• Use of probiotics, prebiotics, or antibiotics within the last three months
• Known allergy to elderberry or its components

Individual participant data will not be shared due to ethical and privacy concerns. The study protocol did not include participant consent for open data sharing, and the dataset contains potentially identifiable health information.

Participants will be randomly assigned to intervention or placebo groups using computer-generated permuted block randomization (block size = 4). Allocation sequences will be created by an independent researcher. Gums will be packaged in identical blister packs labeled with alphanumeric codes that do not reveal group assignment. Only the randomization coordinator will have access to the allocation key. Investigators and outcome assessors will be blinded throughout the study. Cognitive tests and saliva sampling will be conducted by trained staff unaware of group assignment, under standardized conditions.