Background:
Dual use of tobacco products such as cigarettes and water pipe may be associated with increased risk of nicotine dependence and smoking-related complications. Accurate statistics are not available in this regard in Iran. Thus, this study sought to assess the prevalence of dual cigarette/water pipe smoking and its related factors in Iran.

Methods:
This cross-sectional study was conducted on Tehran residents over 15 years of age selected via cluster, multi-stage randomized sampling from different geographical districts of Tehran in November and December 2014. The data were collected using the water pipe section of the Global Adult Tobacco Survey (GATS) questionnaire.

Results:
A total of 1,830 individuals participated in this study; of which, 243 (13.3%) were exclusive water pipe smokers, 76 (4.2%) were dual smokers of cigarettes and water pipe and 120 (6.6%) were exclusive cigarette smokers. Of dual smokers, 86.8% were males and 13.2% were females (P< 0.001). The mean age was 28.01±8.7 yearsin exclusive water pipe smokers and 33.1±1.1 yearsin dual smokers (P< 0.001). Male sex (adj. OR: 3.8) and older age (adj. OR: 1.06) increased the odds of dual smoking.

Conclusions:
The prevalence of dual smoking and exclusive water pipe smoking was 4.2% and 13.3%, respectively. Exclusive cigarette smoking had a prevalence of 6.1%. The frequency of dual smoking of cigarettes and water pipe was considerably high. Dual smokers had a higher mean age than exclusive water pipe smokers and they were mostly males. The mean age at initiation of water pipe smoking in dual smokers was lower than the mean age at the onset of cigarette smoking. In other words, dual smokers started water pipe smoking sooner than cigarette smoking. Future studies with different methodologies are required to further scrutinize the relationship of water pipe and cigarette smoking.