As populations age globally, three conditions increasingly burden older adults: frailty (overall weakness and vulnerability), sarcopenia (progressive muscle loss), and neurocognitive disorders (including dementia). These conditions severely impact quality of life and healthcare costs. Recent research has highlighted the gut microbiome's role in aging, but the oral microbiome—bacteria living in the mouth—has received far less attention despite potential biological plausibility: oral bacteria can influence systemic inflammation, nutritional status, and even reach the brain via the bloodstream or vagal nerve, potentially affecting cognition and muscle health.
The authors plan to conduct a scoping review—a broad literature survey that maps the current evidence landscape rather than meta-analytically pooling results. They will systematically search six major databases (Medline, Embase, Cochrane Central, CINAHL, LILACS, Epistemonikos) from inception through December 2025 for studies in any language examining oral microbiome composition in adults aged 65+ with frailty, sarcopenia, or neurocognitive disorders. They'll include randomized controlled trials, cohort studies, case-control designs, and other relevant research. Two independent reviewers will select studies and extract data, with analysis focusing on which oral organisms associate with these conditions and identifying research gaps.
This is important because the oral microbiome is understudied in aging despite being accessible for sampling and potentially modifiable (e.g., through probiotics, oral hygiene). A systematic map of current evidence could reveal whether oral dysbiosis genuinely links to these syndromes or whether observed associations are spurious or confounded by factors like dietary intake or dental health.
Critical limitations are substantial: this is a protocol, not the actual review—no data have been generated yet, so we cannot know what the evidence actually shows or how strong it is. Scoping reviews are exploratory and deliberately avoid quality assessment or causal claims; they describe 'what exists in the literature' rather than 'what is true.' The heterogeneity of study designs included (RCTs to case studies) means evidence quality may be highly mixed. Publication bias may skew results toward positive associations. The authors also plan to include any-language studies, which increases accessibility but complicates quality appraisal.
For longevity research, this review could be valuable in identifying whether oral dysbiosis is a genuine novel target for aging interventions or whether attention should remain on gut and systemic microbiome modifications. However, the field is still nascent—many oral-aging associations may not yet be published—and causality remains unclear. This protocol is a necessary foundation, but the real scientific value emerges only once the full review is published (expected 2026 or later).
The study represents responsible science communication: the authors preregistered a scoping review protocol, increasing transparency and preventing selective reporting. However, readers should manage expectations: this describes a future literature survey, not a clinical finding or mechanistic discovery.
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