Aging and Salivary Cytokine Concentrations as Predictors of Whole Saliva Flow Rates among Women

Abstract

Introduction: How aging influences the secretion of saliva is not entirely clear. Postmortem studies have demonstrated that, with age, the parenchyma of the salivary glands is gradually replaced by fat, connective tissue, and oncocytes. However, functional studies among healthy individuals indicate that aging per se does not lead to a diminution in the capacity of these glands to produce saliva. To date, the ambiguity between the morphometric and the clinical evidence cannot be explained. The purpose of this study was to determine if there was any relationship between the cytokine concentrations, salivary flow rates and aging. Methods: The study group consisted of 50 racially mixed women between the ages of 18 and 90. SWS were collected for 5 min using a 1-cm3 cube of paraffin as a stimulant. The samples were aliquoted, then frozen until assayed. Cytokine concentrations were determined using ELISA kits. The statistical analysis consisted of descriptive statistics, mean comparisons, and regression analyses. Results: The results suggest a reduction in SWS in association with an increase of salivary TGF-β1 concentrations. The overall model demonstrated an ability of the independent variables to predict the dependent variable (SWS) at the R2 = 0.53 level. The addition of the salivary cytokines to the model suggests that TGF-β1 (p < 0.045) and a near significant IL-2 (p < 0.07) concentration best explain the decrease in salivary function. The statistical relationship is supported by the physiological relationship between TGF-β1, IL-2, apoptosis, and aging. Conclusion: The results suggest a reduction in SWS flow in association with an increase of salivary TGF-β1 concentrations. This reduction concurs with the histomorphometric investigations, which indicate an age-related reduction of acinar cells in salivary gland tissues.