Nasal cavity microbial makeup and the influence on psychiatric symptoms following fire exposure in firefighters

Firefighters experience high levels of occupational stress and trauma, increasing their risk of depression, anxiety, and post-traumatic stress disorder (PTSD). Although microbial communities may influence brain function and behavior through neural pathways, the nasal microbiome remains understudied. This study examined associations between nasal microbiome characteristics and psychiatric symptoms among firefighters.

We conducted a cross-sectional study of 34 firefighters recruited from Texas fire stations. Participants completed validated questionnaires assessing depression, anxiety, and PTSD. Nasal swabs were collected before and after fire suppression and 16S rRNA sequencing was used to characterize microbial communities. Alpha and beta diversity, relative abundance, and differential microbial associations with psychiatric outcomes were assessed using logistic, linear, and linear mixed regression methods.

Sixteen participants (47%) met criteria for depression, six (18%) for anxiety, and four (12%) for PTSD. Alpha diversity was significantly lower in individuals with anxiety (adjusted p = 0.04) while there were no differences in beta diversity or differences in either diversity for PTSD or depression. Increased abundance of the genus Ruminococcus was associated with increased odds of anxiety, while Hydrotalea was associated with PTSD. Depression scores were positively associated with several genera including Aerococcus (1.22; 95%CI: 0.43-2.02) and Dermabacter (1.50; 95% CI: 0.37-2.63). Fire suppression was associated with increased Enhydrobacter (2.08; 95% CI: 0.80 to 3.46) and decreased Hymenobacter (-1.25; 95% CI: -2.22 to -0.27) abundance.

This study identifies preliminary links between nasal microbiome composition and psychiatric symptoms in firefighters and suggests that fire suppression may alter nasal microbial communities.