Income-related inequalities affect the association between obesity and periodontal disease: A cross-sectional analysis in Tokyo Metropolitan Districts

Objectives Obesity is a risk factor for periodontal disease and is associated with socioeconomic status (SES). However, it remains unclear whether SES modifies the relationship between obesity and periodontal disease. This study aimed to investigate the influence of SES on the association between obesity and periodontal disease. Material and Methods We used multilevel Poisson regression, adjusted for SES, to analyze the body mass index (BMI) and periodontal parameters of 962 participants (mean age 58.3 years; SD: 13.8). SES was assessed based on the average income and education levels of their residential areas. Results A significant association was observed between obesity and the proportion of teeth with probing pocket depth (PPD) ≥ 4 mm (ratio of means [RM]: 1.25, 95% confidence interval [CI]: 1.15, 1.38, p  < 0.001), whereas the higher-income group exhibited a significantly lower proportion of teeth with PPD ≥ 4 mm (RM: 0.86, 95% CI: 0.77, 0.96, p  = 0.007). Interaction analysis also revealed a significant interaction between obesity and the high-income group regarding the proportion of teeth with PPD ≥ 4 mm. The subgroup analysis demonstrated that the RM of obesity for the proportion of teeth with PPD ≥ 4 mm was higher in females than in males. Conclusions Income-related inequalities affect the association between obesity and periodontal disease. Among obese adults, those with low-to-middle-income levels may have a higher risk of periodontal disease than those with high-incomes. Clinical Relevance Comprehensive care and oral health education should be enhanced for obese individuals in low-income populations to mitigate their elevated risk of periodontal disease.