Nasal microbiome in relation to olfactory dysfunction and cognitive decline in older adults
Song et al./Nature/2025
Why It Matters
This caught my attention because it suggests the nasal microbiome might be a missing link between smell loss and dementia risk. We've known for years that losing your sense of smell predicts cognitive decline, but this is the first time I've seen data connecting specific nasal bacteria to both. If these patterns hold up in larger studies, nasal microbiome testing could potentially identify people at risk before cognitive symptoms appear.
Key Findings
- 142 older adults (average age ~73) underwent olfactory testing, nasal microbiome sampling, and cognitive assessments
- People with olfactory dysfunction showed different nasal bacterial communities compared to those with normal smell function
- Specific nasal microbiome compositions were associated with performance on cognitive tests measuring memory and executive function
- The relationship between smell loss and cognition may be mediated through the nasal microbiome rather than being a direct effect
- This is observational cross-sectional data — it shows correlation but cannot prove the microbiome causes cognitive changes