In the present study, the lifetime, last year and past 30 day prevalence of hookah smoking were determined to be 26.6%, 17.8% and 8.9%, respectively. The prevalence of hookah smoking in the present study is similar to other studies conducted among university students in Iran (
20,
21). For example, the prevalence of lifetime and last year smoking of hookah were reported to be 30% and 20.7%, respectively, in one study (
20) and in another study 28.7% of males and 11.5% of females reported current hookah smoking (
21). In addition, the prevalence of hookah smoking among students of Zanjan (occasionally and regular use) and Tabriz (last use) Universities, Iran, were reported as 13%, 4.2% and 8.5%, respectively (
22,
23). This rate is even lower than that reported in some other Islamic countries. For example, the lifetime and past-30- day prevalence of hookah smoking have been reported to be 61.1% and 42.7%, respectively for university students of Jordan (
14). Also, in a study among medical and nonmedical university students in Turkey, the total prevalence rate of hookah smoking was found to be 32.7% (
24). In Eastern Mediterranean countries, it seems that hookah smoking has been surged considerably (
25).
Our findings are also relatively low in comparison with studies conducted in western countries. The prevalence of last year hookah smoking among university students has been reported as 25.7% in monitoring the future (MTF) study in US (
26). In north Carolina this rate have been reported as 40% (life time prevalence) and 17% (last 30 day prevalence) (
27). Among students of a university in United States, the lifetime, last year and past 30 day prevalence rates of hookah smoking was reported as 40.5%, 30.6% and 9.5%, respectively (
28). In a British university prevalence of hookah smoking was found to be 38% (lifetime) and 8% (regularly smoking) (
29). The results of a review showed that the prevalence of last month hookah smoking range from 6% to 34% among Middle Eastern adolescents and from 5% to 17% among American adolescents (
25). This high prevalence has been attributed to its social acceptance (
30,
31). In addition, another factor that influences the spread of hookah smoking is that it is perceived to be less lethal and addicting than cigarette smoking (
5,
6). Our findings, like previous studies from Iran and other countries (
4,
29,
32,
33), showed that hookah smoking is more prevalent in men than in women. The logistic regression models demonstrated that odds of hookah smoking are 2.8 for males compared to females. It should be noted that this difference is much higher in the case of cigarette smoking, alcohol and other illegal drug use. It highlights this fact that female students show higher tendency to hookah smoking than to other substances. This might be resulted from high social acceptance of hookah. In Iran, even many religious families do not consider hookah use by women as abnormal.
We found that students who had smoked cigarettes and those who had used alcohol in the last year were more likely to use hookah compared with nonsmokers. Due to the cross-sectional nature of the study, we were not able to identify the temporal sequence of hookah smoking and the use of other substances. However, considering co-occurrence is one of the most effective approaches in prevention of high-risk behaviours. Numerous studies have emphasized the co-occurrence of hookah smoking and other risky behaviours (
34-
36). Several studies indicated that involvement in one risky behavior is related with engagement in other risky behaviours (
37,
38). This may be especially important for the hookah and cigarette smoking; because in both tobacco is used by means of smoking (
39).
Our findings indicated that hookah smoking was strongly associated with cigarette or hookah smoking by friends. One of the most important factors that can affect the spread of hookah smoking is peers’ influence (
3). Heinz et al. showed that participants who were hookah users, as compared to nonusers, had a greater number of friends who had tried and approved hookah use (
35). In addition, several studies indicate that if substance use is common in majority of friends, these youths probably will be pushed to consumption (
40,
41). It is also found that alcohol use and illicit substance use in friends are associated with hookah use among students. Hookah smoking is often a social phenomenon that occurs between friends and predominantly in cafes and bars (
2,
5). Ghafouri et al. in a study among students of health sciences, stated that hookah smoking was perceived as a social activity among friends (
42). Because of religious and legal prohibition of alcohol use in Iran, there is no social drinking in cafes and bars. In such a case, hookah smoking has considerable importance and acts as a mean of socialization for the youth.
In the present study, it was found that hookah smoking is higher in those students with hookah smoking in family. Some studies have emphasized on parents’ substance abuse and increased chance of illicit substance use in children (
43,
44). The role of family members in hookah smoking is complex and notable. The result of a study among Michigan adults found that having a father, mother, or sibling who smoke hookah at home is a significant risk factor for hookah smoking (
45).
5.1. Limitations
This study has some limitations. Due to the cross-sectional design of the study, causal inference of our results cannot be identified. Furthermore, findings of the study are relied on self-report data and it was assumed that the students were honest in answering the questions. For future studies, longitudinal studies are required to determine and monitor the incidence rate of hookah use and its correlates among medical university students.
5.2. Conclusions
The results of this study indicate lifetime, last year and last month use of hookah smoking among students of Tehran University of Medical Sciences. Our findings show a relatively low prevalence of hookah smoking among Iranian students in comparison to other studies. Some factors associated with hookah smoking were identified in this study. The findings of this study can be used for planning and evaluating interventions by considering co-occurrence of hookah smoking with other risky behaviours.