Application of Mixture Cure with the Doubly Censoring Model in Estimation of Initiation Age and Prevalence of Water-Pipe Smoking in Iran: a New Approach in Population-Based Studies

Background The initiation age and prevalence of smoking water-pipe are two important parameters for establishing preventive policies. Thus, the present study was conducted to introduce a new approach for estimating and evaluating the effect of demographic variables on the initiation age and prevalence of smoking water-pipe. Materials and methods The STEPwise approach for non-communicable disease risk factors surveillance (STEPS) 2011 data were used and daily smokers and non-smokers with the age range of 16 to 70 years were included in the study. A survival mixture cure rate model with doubly censoring was used. Results Totally, 9764 individuals were enrolled in the study. No significant association was observed between the initiation age and gender (HR=1.07, 95% CI: 0.76, 1.58), whereas there was a significant difference between initiation age and area of residence (HR=0.62, 95% CI: 0.44, 0.88). The mean age of starting smoking was 25.82 years (95% CI: 24.13, 27.63). The odds of smoking in men were higher than in women (OR=2.34, 95% CI: 1.79, 3.7). The prevalence of smoking had a significant association with socioeconomic status (OR=0.84, 95% CI: 0.72, 0.97), but no association with the level of education (OR=1.06, 95% CI: 0.97, 1.15) and place of residence (OR=1.2, 95% CI: 0.93, 1.57) was found. The estimated prevalence of smoking water-pipe in total, men, and women was 4.8% (95% CI: 4.19%, 5.51%), 7.77% (95% CI: 6.76%, 8.86%), and 3.47% (95% CI: 2.8%, 4.25%). Conclusion A new statistical methodology was applied to estimate and evaluate the effect of demographic variables on the initiation age and prevalence of water-pipe smoking.