Subconcussive head impacts sustained during American football alter gut microbiome diversity and composition

Subconcussive head impacts (SHIs) are a public health concern amongst at-risk populations. SHIs are hits to the head that do not typically generate symptoms and are unlikely to meet diagnostic criteria for mild traumatic brain injury (mTBI). Changes in the gut microbiome have been associated with mTBIs and implicated in both acute recovery from and neurodegenerative pathologies associated with repeated mTBI. This study monitored the gut microbiomes and head impact exposure of collegiate American football players across a competition season to determine if SHIs lead to acute and longer-term changes to the gut microbiome. SHI exposure correlates with changes in microbial diversity and composition three days post-exposure, the athletes gut microbiomes change significantly across the season, and mixed effects modeling provides evidence for cumulative effects of SHIs. These data provide the first evidence for a link between SHIs and changes in the diversity and composition of the gut microbiome.