The effect of demographic characteristics on the relationship between smoking and dry mouth in Iran: a cross-sectional, case-control study.

Objectives: The effect of age, sex, and other demographic factors on the relationship between smoking and dry mouth remains unknown. The aim of this study was to investigate the effects of demographic characteristics on the relationship between dry mouth, also known as xerostomia, and smoking.

Methods: This case-control study included 5,640 randomly-selected subjects from the second phase of the Kerman Coronary Artery Disease Risk Factors Study, which observed 10,000 participants from 2014 to 2018. A checklist was used to record the participants' demographic characteristics and smoking frequency. Each participant completed a six-item Fox questionnaire to measure dry mouth as a dependent variable. The interaction terms of daily cigarette smoking with sex, age, educational level, and marital status were entered into the model. Non-significant terms were removed using hierarchical model selection.

Results: Of the sample, 3,429 (60.8%) did not have dry mouth and were analyzed as controls, whereas 2,211 (39.2%) had xerostomia and were deemed to be cases. Smokers were more likely to have dry mouth in all ages and both sexes (p < 0.001). As male became older, the chance of having dry mouth increased more rapidly than among female smokers (p < 0.001). In addition, female smokers were more likely to have dry mouth than male smokers (p < 0.001).

Conclusions: The likelihood of dry mouth among daily smokers depended on age and sex. Female smokers were more likely to have dry mouth, and its likelihood increased with age in daily smokers of both sexes, though more rapidly in males.