INTRODUCTION: This cross-sectional study aimed to investigate the associations between serum homocysteine levels and missing teeth, as well as to explore the threshold effect of serum homocysteine levels on the number of missing teeth. MATERIALS AND METHODS: This study involved 4746 participants (aged ≥ 40 years) from NHANES data 2003-2006. Negative binomial regression was used to assess the association between serum homocysteine levels and tooth loss. Non-linear and dose-response relationships were analyzed using smooth curve fitting and threshold effect analysis. In addition, we supplemented the relationship between serum homocysteine levels and tooth loss and conducted subgroup analysis to determine the impact of covariates on the relationship between serum homocysteine levels and tooth loss. RESULTS: In a fully adjusted negative binomial regression model, higher levels of serum Hcy concentration in the Q2-Q4(Q2: IRR = 1.46, 95%CI (1.67,1.79))
Q3: IRR = 1.42, 95%CI (1.36,1.48)
Q4: IRR = 1.47,95%CI (1.01,1.78)) groups increased the likelihood of tooth loss compared with quartile Q1 (low level of serum homocysteine). Threshold effect analysis revealed that the log2-transformed Hcy infection point was at 2.95 μmol/L. CONCLUSION: The likelihood of tooth loss increased by 47% for each unit increase in serum homocysteine level. There was a non-linear positive correlation between serum homocysteine and tooth loss, with a threshold effect of approximately log2(Hcy) = 2.95 μmol/L. This link emphasizes the importance of maintaining appropriate homocysteine levels to prevent oral health problems.