The positive association between hemoglobin A1c and the prevalence of periodontitis: A cross-sectional study from NHANES 2009 to 2014

Periodontitis is a common chronic inflammatory disease. Hemoglobin A1c (HbA1c) is a key biomarker for long-term glycemic control and has recently been suggested to play a role in the occurrence and progression of periodontitis. However, previous studies have yielded inconclusive results due to limited sample sizes and inconsistent analytical methods. This study aimed to investigate the relationship between HbA1c levels and the prevalence of periodontitis using data from NHANES 2009 to 2014. Periodontitis was defined according to the criteria of the Centers for Disease Control and Prevention and the American Academy of Periodontology. HbA1c was analyzed both as a continuous and categorical variable. Complex survey-weighted logistic regression models were applied to evaluate the associations, and restricted cubic spline regression was used to assess potential dose–response relationships. Subgroup and sensitivity analyses were conducted to further examine the robustness of the findings. A total of 4166 participants were included, with a mean age of 52.0 ± 14.2 years; 2081 were male and 2085 were female. The overall prevalence of periodontitis was 54.7% (2280/4166). Higher HbA1c levels were significantly and positively associated with the prevalence of periodontitis. In the fully adjusted model, each 1% increase in HbA1c was associated with an 18% higher odds of periodontitis (OR = 1.18, 95% CI: 1.03–1.35). Compared with participants with HbA1c < 5.7%, those with HbA1c of 5.7% to 6.4% and ≥ 6.5% had approximately 36% and 75% higher odds, respectively. Restricted cubic spline analysis indicated a linear dose–response relationship between HbA1c and periodontitis. Subgroup analyses showed that the positive association between HbA1c and periodontitis remained significant among males, Mexican Americans, individuals with low income, nondiabetic participants, and those with daily alcohol intake < 10 g/day. Sensitivity analyses confirmed the robustness of the results. Elevated HbA1c levels are significantly and positively associated with the prevalence of periodontitis, suggesting that HbA1c may serve as a potential marker for monitoring periodontal health. Blood glucose control should be considered in the prevention and management of periodontitis, with increased attention to high-risk populations. However, due to the cross-sectional design, causality cannot be inferred from these findings.