# Estimating the Causal Effect of Tooth Loss on the Critical Outcome of COVID-19

## TL;DR

This study finds that tooth loss is linked to a higher risk of severe outcomes from COVID-19, such as ICU admission or death.

## Contribution

The study demonstrates a causal link between tooth loss and critical outcomes of COVID-19 using three propensity score methods.

## Key findings

- Tooth loss was associated with a higher risk of ICU admission or death from COVID-19.
- The association remained significant across all three propensity score methods used.
- The findings suggest that oral health is an important factor in predicting severe outcomes of COVID-19.

## Abstract

The objective of this study is to estimate the causal effect of tooth loss on the critical outcome of COVID-19, using 3 different propensity score methods. This retrospective study included patients aged >35 y with a diagnosis of COVID-19 between January 2020 and July 2021 at 2 hospitals in the Netherlands. The independent variable was number of teeth, dichotomized into 0 to 20 teeth (treatment) and 21 to 28 teeth (control). The critical outcome of COVID-19 (intensive care unit [ICU] admission and/or death) was the dependent variable. Potential confounders included patients’ demographics, lifestyle habits, medical conditions, COVID-19–related parameters, and hospitals. Three different propensity score methods were used to balance the baseline characteristics between the treatment and control groups: including propensity score matching (PSM), inverse propensity score weighting (IPW), and marginal mean weighting through stratification (MMWS). Both univariate and multivariate logistic regression analyses were performed to assess the causal association between tooth loss and the critical outcome of COVID-19 after the propensity methods. A total of 399 patients were included in the analyses. The multivariate logistic regression analysis controlling for the confounders revealed a statistically significant association between tooth loss and the critical outcome of COVID-19 across all the 3 propensity score methods: PSM (causal risk ratio [cRR]: 2.00; 95% confidence interval [CI]: 1.07–3.74; P = 0.03), MMWS (cRR: 1.78; 95% CI: 1.07–2.06; P = 0.03), and IPW (cRR: 1.85; 95% CI: 1.09–3.15; P = 0.02). Tooth loss has a statistically significant causal effect on the critical outcome of COVID-19. Patients with fewer teeth have a higher risk of ICU admission or mortality due to COVID-19.

The findings of this study can help clinicians and policymakers recognize the important role of oral health in COVID-19 prognosis. By encouraging health care professionals to integrate oral health assessments into comprehensive evaluations, the study promotes more accurate risk stratification for COVID-19 prognosis. This enables early interventions and better management of high-risk patients, ultimately leading to improved health outcomes by preventing critical outcomes of COVID-19 and enhancing patient care.