Tooth Retention in US Adults: a Quantile Regression Analysis

Abstract

<p><strong>Objectives</strong>: The number of natural teeth (NT) retained is closely associated with aging and oral health status. The traditional ordinary least-square (OLS) regression model is commonly used for analyzing NT. However, the variance of NT would change with covariates such as age, which violates the ‘equal variance’ assumption of the OLS regression. In contrast, quantile regression is not limited by this assumption and can model the relationship between quantiles of the dependent variable and covariates. This study aimed to use quantile regression to explore the effect of sociodemographic factors and smoking on NT.<br><strong>Methods</strong>: Data from the NHANES 2017-2020 were used. Adults ≥30 years were included. NT was measured by the number of natural permanent teeth. Weighted quantile regression was used to estimate and compare the effects of covariates (age, gender, race/ethnicity, education level, income level, and smoking status) on different quantiles of NT. Quantile regression models were fitted from Q10 (10th quantile) to Q90 by every 5 quantiles.<br><strong>Results</strong>: Altogether, 2,307 complete cases were analyzed, representing 67,855,791 civilian noninstitutionalized U.S. residents. Aging was more negatively associated with NT in lower quantiles. Every one-year increase in age was associated with 0.26 (95% CI, 0.23-0.30) fewer teeth at Q25. However, this estimate decreased to 0.13 (95% CI, 0.11-0.15) at Q50 (median) and 0.06 (95% CI, 0.05-0.08) at Q75. Gender had insignificant and similar effects on NT across quantiles, but education level, income, and smoking status exerted a greater influence on NT in lower quantile levels. Hispanic individuals preserved a maximum of 2.91 (95% CI, 1.68-3.67) more teeth than non-Hispanic white (NH-white) individuals at Q10. NH-black lost 1.67 (95% CI, 0.87-2.30) more teeth than NH-white at Q40, but this discrepancy dwindled toward Q10 and Q90.<br><strong>Conclusions</strong>: Generally, the effects of covariates on NT could be more prominent among those with fewer teeth.<br></p>