Association between Salivary pH and Estimated Glomerular Filtration Rate Status in a Community-Dwelling Population: A Cross-Sectional Study.

INTRODUCTION

Globally, chronic kidney disease (CKD) is a common condition associated with several complications and high mortality. Early detection and monitoring of CKD is important for prolonging healthy life expectancy. Salivary pH is reported to increase in patients with chronic renal failure; however, the association between salivary pH and the estimated glomerular filtration rate (eGFR) status, which is usually considered to assess kidney function in clinical settings, has not been adequately studied. Therefore, this study aimed to examine the association between salivary pH and eGFR through multivariate analysis.

METHODS

We conducted a cross-sectional study using the data from a community-based cohort study conducted between 2017 and 2019 in Japan. We aimed to develop a prediction model to determine the eGFR status using salivary pH, instead of blood urea nitrogen (BUN), in combination with self-reported information (age, sex, body mass index, disease history, medication, and lifestyle) in 1,056 subjects (433 men and 623 women) who participated in the study in 2017. We first identified the logistic model including several explanatory variables in addition to BUN (BUN model) and also developed the logistic model that replaced BUN with salivary pH (pH model). We examined the predictive accuracy of the two developed models using the validation data of 298 subjects (116 men and 182 women) who participated in the study in 2019.

RESULTS

BUN and salivary pH were significantly associated with the eGFR status (odds ratio [ORs]: 1.24, 95% confidence interval [CI]: 1.17-1.32, p < 0.001 for BUN; ORs: 0.96, 95% CI: 0.94-0.98, p < 0.001 for salivary pH, respectively). The developed pH model included age, kidney disease history, diabetes history, habitual medication for hypertension, habitual alcohol consumption status, and habitual exercise status in addition to salivary pH. The pH model showed accuracy comparable to that of the BUN model in determining the eGFR status (area under the curve for the pH and BUN models was 0.796 and 0.799, respectively; p = 0.933).

CONCLUSION

This study clarified the association between salivary pH and the eGFR status.