Microbiome substudy
At CHEST 2023, Ms. Lam reported on microbiome pilot and validation substudies of FIREHOUSE.
The pilot study included five patients in each arm. The validation sample included 15 participants in the Mediterranean diet group and 16 in the usual-care diet group.
Each participant’s microbiome was assessed with genomic sequencing with sequences aligned to a bacterial database. The number and diversity of bacterial species in each sample were determined with the Chao1 Index and Shannon Index, respectively.
There were no significant differences among the study groups in mean age, exposure at the World Trade Center site, or years of service.
Although bacterial diversity did not differ between the study arms either at baseline or at 6 months, in both groups it significantly decreased over time (P = .02 in the pilot, P < .0001 in the validation arm).
In the pilot study, there was an increase over 6 months in the usual care arm only of Bilophila wadsworthia, a species associated with high-fat diets and inflammation.
In the validation study, patients in the LoCalMed arm had significant reductions in Ruminococcaceae (P = .015) and increases in both Bacteroides ovatus (P = .03) and Alistipes shahii (P = .038), a recently identified species with uncertain protective or pathogenic potential.
In contrast, there were no significant increases in species in the usual-care group, but there were significant declines in several other bacterial species; Ms.Lam, however, did not say whether these changes had clinical significance. “Future studies will assess microbial association with clinical outcomes,” Ms. Lam said.
Confounding factors
Samuel Evans, MD, a pulmonologist at Straub Medical Center in Honolulu who moderated the oral abstract session where the data were presented, commented that the data are interesting but added that associations are difficult to determine given the heterogeneity of exposures that firefighters encounter.
“I think it’s interesting that clearly diet is influencing the type of bacteria in the biome in the gut, and perhaps some are favorable, and some are not favorable,” he told this news organization “We already know that the Mediterranean diet is associated with better health outcomes, so it makes sense, but can we tease out in the microbiome which bacteria are harmful and which are helpful.”
He noted that there are a lot of confounding factors and that “it’s hard to find the right signal when you have so many variables.”
The FIREHOUSE study is supported by the Centers for Disease Control and Prevention’s National Institute of Occupational Safety & Health and the National Heart, Lung, and Blood Institute. Ms. Lam, Dr. Nolan, and Dr. Evans report no relevant financial relationships.
A version of this article first appeared on Medscape.com.