Direct effect of common mental disorders on xerostomia in adults estimated by marginal structural models: A population‐based study

Abstract

To investigate the controlled direct effect (CDE) of common mental disorders (CMD) on xerostomia which is not mediated by psychoactive medication intake. A population-based cross-sectional study was conducted with 1720 individuals aged 20-59years from Florianópolis, Brazil, in 2009. A two-stage cluster sample design was adopted, with a systematic selection of census tracts, followed by a random selection of households. All inhabitants of the selected households belonging to the age group of interest were considered eligible to participate. CMD were assessed using the Self-Reporting Questionnaire (SRQ>7). Xerostomia was the outcome assessed by asking: "How often do you feel dry mouth?" with responses "often" and "always" taken as indicating xerostomia. Psychoactive medication intake was set as the mediator. Confounding factors included sex, age, per capita family income, educational attainment and smoking status. Marginal structural models were performed to quantify the CDE of CMD on xerostomia. Missing data were handled by multiple imputation by chained equations, and sensitivity analysis for unmeasured confounding was carried out. The overall prevalence of xerostomia was 8.8% and 15.3% of the individuals presented with CMD. After adjustment, the prevalence of xerostomia among individuals with CMD was 3.2 times higher than that among individuals without CMD (PR=3.2 [95% CI: 2.3; 4.5]). The CDE of CMD on xerostomia which is not mediated by the medication intake resulted in a three times greater prevalence of xerostomia (PR=3.0 95% CI: 2.0; 4.5) among those individuals with CMD. Common mental disorders is directly and negatively associated with xerostomia. Clinicians should bear in mind the emotional state when investigating the underlying factors and managing patients with xerostomia.