Axillary microbiota is associated with cognitive impairment in parkinson's disease patients

Cognitive impairment (CI) is among the most common non-motor symptoms of Parkinson's disease (PD), with a substantially negative impact on patient management and outcome. The development and progression of CI exhibits high interindividual variability, which requires better diagnostic and monitoring strategies. PD patients often display sweating disorders resulting from autonomic dysfunction, which has been associated with CI. Because the axillary microbiota is known to change with humidity level and sweat composition, we hypothesized that the axillary microbiota of PD patients shifts in association with CI progression, and thus can be used as a proxy for classification of CI stages in PD. We compared the axillary microbiota compositions of 103 PD patients (55 PD patients with dementia [PDD] and 48 PD patients with mild cognitive impairment [PD-MCI]) and 26 cognitively normal healthy controls (HC). We found that axillary microbiota profiles differentiate HC, PD-MCI, and PDD groups based on differential ranking analysis, and detected an increasing trend in the log ratio of Corynebacterium to Anaerococcus in progression from HC to PDD. In addition, phylogenetic factorization revealed that the depletion of the Anaerococcus, Peptoniphilus, and W5053 genera is associated with PD-MCI and PDD. Moreover, functional predictions suggested significant increases in myo-inositol degradation, ergothioneine biosynthesis, propionate biosynthesis, menaquinone biosynthesis, and the proportion of aerobic bacteria and biofilm formation capacity, in parallel to increasing CI. Our results suggest that alterations in axillary microbiota are associated with CI in PD. Thus, axillary microbiota has the potential to be exploited as a noninvasive tool in the development of novel strategies.