Salivary microbiota signatures of periodontitis are associated with CGM-derived short-term glycaemic control in adults with type 1 diabetes: a pilot study

Aims Periodontitis is common in type 1 diabetes (T1D), yet its relationship with short-term glycaemic control remains unclear. Continuous glucose monitoring (CGM) provides complementary metrics to HbA1c, including Time in Range (TIR) and Time Above Range (TAR). We investigated whether periodontitis-associated salivary microbiota signatures are associated with CGM-derived short-term glycaemic metrics in adults with T1D. Methods In this pilot cross-sectional study, 24 adults with T1D were classified using the Community Periodontal Index as gingivitis (CPI 1-2; n=12) or periodontitis (CPI 3-4; n=12). Oral indices, HbA1c and CGM metrics were collected. Salivary microbiota was profiled by 16S rRNA gene sequencing. Differential abundance, inferred functional profiling, and multivariate association analyses were used to relate microbial signatures to CGM metrics. Results Compared with gingivitis, periodontitis was significantly associated with lower TIR (40.5% vs 67.7%; p=0.004) and higher TAR (54.4% vs 28.9%; p=0.01), despite similar HbA1c. Gingivitis microbiota was enriched in Neisseria and Lautropia and associated with higher TIR, whereas Filifactor and the Eubacterium saphenum group were more found in periodontitis and associated with higher TAR. Predicted functional pathways in periodontitis were led more towards fermentative pathways and amino acid biosynthesis. Conclusions In this cohort of adults with T1D, periodontitis was associated with distinct salivary microbiota signatures varied along with CGM-derived short-term glycaemic metrics, despite similar HbA1c. If confirmed in larger longitudinal studies, salivary profiling may be an interesting complement for CGM-based assessment to support integrated periodontal and metabolic follow-up.