Background: The potential influence of oral bacteria with high inflammation potency (e.g. hexa-acylated lipid A) on rate of lung function (LF) decline in the general population, which is important for assessing respiratory health, remains unexplored.

Methods: Participants (n=209) from the RHINESSA community-based study population in Bergen, Norway (mean age: 28.8 years; 44% women) were included based on availability of i. LF data (reported as Z-scores) collected at baseline (2013-15) and follow-up (2020-21) and ii. baseline gingival samples. 16S rRNA amplicon sequencing was performed for bacterial community/lipid A profiling (gingiva). LAL assay was performed for a subset (n=88) for endotoxin quantification (saliva). Linear regression models stratified by sex were used to examine the association between the baseline microbiota and LF at follow-up, with adjustments for baseline LF, and weight and smoking status at follow-up.  

Results: Bacterial richness was positively associated with FVC, but negatively associated with FEV1/FVC in females only (p<0.005). Bacterial diversity and salivary endotoxin loads were not significantly associated with LF for either sex. In females, taxa with the hexa-acylated lipid A were positively associated with FEV1/FVC. Conversely, in males, taxa with penta-acylated lipid A were positively associated with FEV1 and FVC (p<0.005). Kocuria was negatively associated with FEV1 and FVC for both sexes.  

Conclusions: The association between oral bacteria and respiratory health appears to be gender dependent. Further analyses are needed to determine whether specific genera are driving the gender specific associations observed.