Lower diversity in the oral microbiome was associated with worse cognitive function in schizophrenia sufferers in a new study.
Researchers from the Institute of Science Tokyo, Japan hypothesised that increased inflammation or changes in essential microbial functions resulting from a lack of microbiome diversity could be linked to poorer cognitive performance.
While previous studies have found an association between the gut microbiome and severity of schizophrenia symptoms, this study shifts the focus to oral bacteria.
Takehiro Tamura, assistant professor at Science Tokyo, said: ‘Host-microbiome interactions are not limited to the gut. Like the gut microbiota, the oral microbiota also participates in such interactions. Its significance in systemic and neurological conditions has become increasingly recognised.’
How was the relationship between schizophrenia and the oral microbiome tested?
To test their hypothesis, the researchers compared the cognitive function and oral microbiome makeup of 68 schizophrenia patients and 32 unaffected individuals.
Overall cognitive performance was measured using the full-scale intelligence quotient (FSIQ), where higher scores indicate better cognitive function. The researchers then analysed saliva samples using rRNA gene sequencing to determine the diversity of the oral microbiome.
The results showed a clear association between oral microbiota diversity and cognitive performance. Patients with schizophrenia had less diverse oral microbiomes and lower levels of cognitive function. Within this group, less microbiome diversity was associated with lower FSIQ.
Tamura said: ‘In people with schizophrenia, lower oral microbiota diversity was associated with poorer cognitive performance… This study offers a new perspective on the oral-brain axis and lays a foundation for future mechanistic studies and intervention research, the latter including studies of oral hygiene measures, prebiotics, and probiotics.’
The study was published in the Schizophrenia Bulletin.
