Self-reported oral health indicators and glycemic status in community-dwelling adults: evidence from the Uonuma cohort study

Background Although oral health has been linked to glycemic outcomes, its association with different stages of glycemic dysregulation remains unclear. This study examined the associations of self-reported periodontal disease history, masticatory ability, and remaining tooth count with HbA1c-based glycemic status among community-dwelling adults. Methods This cross-sectional study used baseline data from the Uonuma CKD Cohort Study, including 4,338 participants aged ≥40 years from Niigata Prefecture, Japan. Oral health indicators included self-reported periodontal disease history, masticatory ability, and remaining tooth count. HbA1c-based glycemic status was classified as normal-range (<5.7%), prediabetes-range (5.7–6.4%), or diabetes-range (≥6.5%). Multinomial logistic regression was used to estimate relative risk ratios (RRRs) and 95% confidence intervals (CIs) for associations with glycemic category across four sequential adjustment models. Poisson regression with robust variance estimation was additionally performed for dysglycemia (HbA1c ≥ 5.7%) as a secondary outcome. Results The median age was 66.0 years, and 53.7% were female. Prediabetes-range and diabetes-range HbA1c were observed in 33.6% and 5.9% of participants, respectively. Periodontal disease history was associated with prediabetes-range HbA1c and dysglycemia in unadjusted and partially adjusted models, but these associations were attenuated after full adjustment. Masticatory ability showed no significant association with any glycemic outcome in adjusted analyses. Edentulous participants had significantly higher RRRs of diabetes-range HbA1c compared to those with ≥20 teeth in unadjusted (RRR: 2.25, 95% CI: 1.35–3.75) and age- and sex-adjusted models [adjusted RRR (aRRR): 1.63, 95% CI: 1.17–2.75], but this association was attenuated after further adjustment. Conclusions Self-reported periodontal disease history was most consistently associated with prediabetes-range HbA1c and dysglycemia, although these associations were attenuated after full adjustment. Tooth loss was associated with diabetes-range HbA1c before full adjustment, suggesting that shared metabolic and lifestyle-related factors may account for part of the observed attenuation. Prospective studies using clinically verified oral health assessments are needed to clarify temporal relationships and potential mechanisms underlying these associations.