The impact of periodontitis exposure misclassification bias from partial‐mouth measurements on association with diabetes and cardiovascular disease

Aim To quantify exposure misclassification bias arising from use of partial‐mouth protocols in studies of periodontitis–systemic disease associations. Materials and Methods Using data from 10,134 adults participating in the National Health and Nutrition Examination Survey, we classified periodontal status based on full‐mouth clinical examinations and three commonly used partial‐mouth protocols. Associations between periodontitis and self‐reported diabetes and cardiovascular disease were evaluated under each protocol using adjusted logistic regression. Percent relative bias was calculated to evaluate magnitude and direction of bias. Results Misclassification primarily resulted in underestimation of associations, the extent of which depended on both the outcome under study and exposure severity. Bias due to misclassification of severe periodontitis was negligible for cardiovascular disease (0%–4.1%) compared to diabetes (177.7%–234.1%). In contrast, bias in moderate periodontitis associations was comparable across each outcome—diabetes (28.4%–39.5%) and cardiovascular disease (8.9%–46.7%). Results did not meaningfully change based on the partial‐mouth protocol implemented. Stratified analyses showed increased bias among those with ≤15 teeth. Use of mean attachment loss as a continuous exposure resulted in minimal‐to‐no bias. Conclusions Exposure misclassification bias due to use of partial‐mouth protocols can yield inaccurate conclusions about periodontitis–systemic disease associations, the extent of which may depend on periodontitis classification and the association under study.