Objectives: The aim of this study was to examine the association between medication exposure and (1) unstimulated whole-salivary flow rate and (2) the severity of xerostomia among older people while adjusting for multiple medication use.
Methods: Data were obtained from participants remaining at the five-year follow-up phase of a cohort study of community-dwelling older South Australians. Medication exposure information was available at baseline and at five years, enabling examination of the effects on dry mouth of long-term exposure to medications. At the five-year follow-up, unstimulated salivary flow was estimated using the spit method, and xerostomia severity was estimated using the 11-item Xerostomia Inventory. Because of the potential difficulties posed by polypharmacy, a two-stage analytical approach was employed: (1) Classification and Regression Tree (CART) analysis was used as an exploratory device to elucidate the relationships among the dependent and independent variables, and (2) linear regression analysis was used as a complementary procedure.
Results: Unstimulated flow rate was lower among individuals who were female or taking antidepressants at both baseline and five years, and higher among smokers or people who were taking hypolipidemic drugs. Xerostomia severity was higher among females, or individuals taking: (1) an anginal at baseline and five years, (2) an anginal without a concomitant betablocker at five years, (3) thyroxine and a diuretic at five years, or (4) antidepressants or antiasthma drugs at both baseline and at five years.
Conclusions: These results suggest that polypharmacy can be accounted for to a certain extent by using CART analysis in conjunction with more conventional approaches; and that the relationship between medications and dry mouth is a complex one, and differs according to which aspect of dry mouth is being examined.