Scalp Bacterial Microbiota Dysbiosis in Androgenetic Alopecia: Community Structure, Functional Profiles, and Associations with Lifestyle Factors

The aim of this study was to explore the scalp bacterial flora structure and functional characteristics in androgenetic alopecia (AGA) patients, analyze its association with disease phenotypes and unhealthy lifestyles, and provide a basis for clarifying AGA’s microecological pathogenic mechanism and targeted interventions. A total of 7 AGA patients and 6 healthy controls (HC) were enrolled, with scalp microbial samples collected. High-throughput sequencing of the 16S rRNA V3–V4 region was used to analyze flora alpha/beta diversity, species composition and differential species. LEfSe and KEGG functional prediction screened marker bacteria and differential pathways, and clinical/lifestyle data were collected for inter-group comparisons. No significant difference in Chao index was observed between groups ( P >0.05), but Shannon/Simpson indices/Pielou evenness ( P <0.01) and intra-group Bray–Curtis distance ( P <0.001) were significantly higher in the AGA group, indicating reduced community stability. Staphylococcus dominated healthy scalps; the AGA group had fewer symbiotic bacteria but enriched Acinetobacter , Pseudomonas , and Cutibacterium . LEfSe identified Firmicutes / Staphylococcus as HC markers and Proteobacteria / Gammaproteobacteria / Acinetobacter / Pseudomonas as AGA dysbiotic flora. KEGG showed upregulated metabolic, immune and cell motility pathways in AGA ( P <0.05), with only infectious diseases pathway enriched in HC. AGA patients had more frequent hair washing and higher rates of staying up late, high-fat diet and insufficient fruits/vegetables (all P <0.05). In conclusion, AGA patients have typical scalp microecological dysbiosis closely related to unhealthy lifestyles, which may accelerate alopecia by inducing follicular inflammation. Scalp flora can be potential biomarkers and targets for AGA assessment and intervention.