The impact of diabetics and smoking on gender differences of smear positive pulmonary tuberculosis incidence

Background Several determinants are responsible for different incidences of smear positive pulmonary tuberculosis (TB). The main determinants are cigarette smoking and diabetes mellitus. The aim of this study is to determine the effect of these risk factors effect modifiers in TB/gender association. Methodology In this retrospective cohort, relative risk of gender in developing smear positive TB as well as its interaction with smoking and diabetes mellitus were investigated. Results Of 1243 smear positive TB cases, 63.2% were male. Prevalences of diabetes mellitus among men and women TB cases were 9.2% and 22.9% respectively (p<0.001). Frequency of cigarette smoking among men was significantly higher than that in women (61.7% vs. 7.6% respectively, p<0.001). Male gender, increased the risk of developing smear positive TB as of 98% and 5% in smokers and non-smokers respectively (p=0.001), indicating an interaction between gender and smoking in the effect on TB. In addition, male gender increased the risk of TB as of 13% and 34% in patients with and without diabetes mellitus respectively (p=0.300) indicating no interaction between gender and diabetes mellitus on TB incidence. Conclusion Our study showed that cigarette smoking is a determinant factor for gender differences in TB incidence but diabetes mellitus does not affect the association between TB and gender.