# Income-related inequalities in the association of obesity and periodontal disease: a register-based cross-sectional analysis in the Tokyo metropolitan districts

## TL;DR

This study finds that income levels influence how obesity affects periodontal disease risk, with lower-income obese individuals facing higher risks.

## Contribution

The study reveals that socioeconomic status modifies the obesity-periodontal disease relationship, particularly in high-income groups.

## Key findings

- Obesity is significantly linked to deeper periodontal pockets, indicating higher disease risk.
- High-income individuals show a lower proportion of severe periodontal pockets despite obesity.
- The obesity-periodontal disease link is stronger in females than in males.

## Abstract

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 investigated the influence of SES on the association between obesity and periodontal disease.

We used multilevel Poisson regression, after adjusting for potential confounding factors including population-level SES, to analyze the body mass index (BMI) and periodontal parameters of 962 participants (mean age 58.3 years; SD: 13.8).

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]: 1.14, 1.37; p < 0.001), whereas the high-income group exhibited a significantly lower proportion of teeth with PPD ≥ 4 mm (RM: 0.84, 95% CI: 0.71, 0.998; p = 0.047). Interaction analysis also revealed a significant interaction between obesity and the high-income group regarding the proportion of teeth with PPD ≥ 4 mm (p = 0.020). 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.

Income-related inequalities are associated with the relationship between obesity and periodontal disease. Among obese adults, those with low- and middle-income levels may have a higher risk of periodontal disease than those with high income.

Comprehensive care and oral health education may be enhanced for obese individuals in low-income populations to mitigate their elevated risk of periodontal disease.

The online version contains supplementary material available at 10.1007/s00784-025-06638-1.