cigarette smoking is the most important preventable cause of mortality all over the world . also , it is responsible for many non - communicable diseases such as cancers and cardiovascular diseases . moreover , cigarette smoking is the cause of half of the death of those who smoke for a long time . in the year 2000 , about 5 million adults died as a result of cigarette consumption ( about 12% of total deaths in the year 2000 ) . it is estimated that this rate reaches 8.3 million per year by the year 2030 , which 70% of these deaths will occur in developing countries . according to the who estimation , there are about 1.3 billion smokers worldwide that comprise one third of the world population over the age of 15 years . if this pattern of smoking remains unchanged , this rate will reach 2 billion by the year 2030 . meysamie a and colleagues reported that prevalence of cigarette smoking is 23.4% and 1.4% in iranian males and females , respectively . teachers and other groups like clergymen who can be role models , play an important role in persuasion or prevention of cigarette smoking among the youth . also , as students will enter the society and play key roles such as physicians , engineers , and teachers and so on ; studying their smoking behaviors is very important . therefore , students are also role model for the younger , as well as being a representative of youth in the population . the rate and tendency toward smoking among students has increased as shown by several studies . for example , a national survey in the us demonstrated that during a 5-year period , the rate of smoking among students increased from 22% to 29% . also , a study in iran found similar results showing that 5% of the female students in medical schools who were non - smokers in their first year of study became cigarette users in their seventh year of education . these rates among male students were 2% in the first and dramatically increased to 34% in the seventh year . heydari et al . also showed that prevalence of smoking was significantly higher in students in their last year of study compared with whom in the first year . in addition , several studies have demonstrated that prevalence of smoking was higher among students who had smoker teachers compared to those who had non - smoker . these imply the importance of study of prevalence of smoking in these groups and also their knowledge , attitude and practice on the matter . since the clergymen in any religion are one of the most influential groups in the society , study of their smoking habits has been of interest and several studies looked at the prevalence of smoking in this group . for example , a study on buddhist monks demonstrated that prevalence of daily smoking was 12% , which was lower than general population . this study also showed that buddhist monks with no history of smoking had a better knowledge and attitude towards the hazards of smoking . however , there is no study about smoking status of clergymen in islamic countries including iran . the aim of this study is to estimate and compare the prevalence of smoking in 3 groups of male teachers , clergymen and university students and also their knowledge , attitude and prediction of future smoking . this is the first study in iran , which compares not only the prevalence of smoking but also evaluates knowledge , attitude and their future prediction of smoking and investigates inter - relationship in these 3 groups . university students , clergymen and teachers were studied in tehran , iran during 2009 . in this cross sectional study , the knowledge , attitude towards tobacco consumption and their prediction of smoking in the next 5 years of participants were asked by questionnaire . since the understudy clergymen were all males , only males first , tehran islamic religious school and shahid beheshti university were randomly selected from the corresponding lists . then , four medical and randomly four non medical faculties from the shahid beheshti university were selected . one class per grade ( from grade 1 to 4 ) was also randomly selected in these faculties . besides , in tehran islamic religious school one class per grade ( from grade 1 to 5 ) was also selected randomly . the students and clergymen were all 18 - 25 years old . in each class , after explaining the aim of the study and also the confidentiality , all the students were invited to participate in the study . male teachers ( 20 - 29 years ) who thought boys in middle schools in tehran were also randomly selected . first , from the list of districts provided by the ministry of education and training 5 districts randomly selected . third , in each school , on average , about 10 teachers were randomly selected . for calculation of the required number of subjects in each of 3 groups , the formula for sample size calculation for proportion was used . considering p = 50% ,  = 0.05 and precision of 0.05 , a minimum sample size of 385 was computed for each group . a total of 1,271 university students were enrolled ( 765 medical and 506 non - medical ) . also , 549 clergymen and 551 teachers were randomly studied . therefore , in all 3 groups , we examined a larger population than the calculated required number , which generally can increase the power and precision of the analysis . to examine knowledge and smoking status of the study subjects , a self - report questionnaire was adapted from the standard questionnaire of the global adult tobacco survey . this questionnaire evaluates age of smoking initiation , place of birth , history of smoking ( one with consumption of at least 100 cigarettes was defined as a smoker person ) , smoking status at present , also knowledge about tobacco consumption ( including 4 general knowledge multiple choice questions with 4 options ) , attitude towards tobacco consumption ( 4 multiple choice questions with 5 options ) and contains one question about the probability of tobacco consumption in the next 5 years , which is presented in details by heydari et al . considering the subjects total scores of knowledge and attitude , the answers were categorized into 2 groups of poor / inappropriate ( no correct answer ) and moderate or good / appropriate ( at least one correct answer ) . the answer to the question about probability of smoking in the next 5 years was divided into 2 groups of yes or no . data was entered and analyzed using spss ( 11.5 ) and stata ( 11.0 ) . chi - squared test and logistic regression were used for comparison of smoking status , knowledge , attitude , and probability of smoking in the next 5 years among the 3 groups . in this study , 1,271 students , 549 clergymen , and 551 teachers were interviewed in tehran during 2009 . as table 1 shows , 395 ( 31.1% ) of students , ( 95% ci : 28.5%-33.6% ) had a history of smoking more than 100 cigarettes . this rate was 21.9% ( 95% ci : 18.3 - 25.3% ) among clergymen and 27.2% ( 95% ci : 23.4%-30.9% ) among teachers . as presented in this table , the highest prevalence was seen among students and the lowest among clergymen ( p < 0.0001 ) . logistic regression showed that prevalence of smoking was significantly higher among students and teachers than clergymen ( p < 0.0001 and p = 0.04 ) . however , the 3.9% difference in prevalence of smoking between students and teachers was not found significant ( p = 0.09 ) . also , among the 3 groups , there was borderline difference in age of smoking initiation ( p = 0.06 ) . neither , such difference was detected in terms of successful quit attempts , occasional smoking and daily cigarette consumption ( p = 0.99 ) . no significant difference was found in the amount of daily smoking ( less than 10 cigarettes , 11 - 20 cigarettes and more than 20 cigarettes ) between the 3 groups ( p = 0.64 ) . smoking status of male students , teachers and clergymen in tehran there was a significant difference between the understudy groups in terms of their knowledge , attitude and probability of smoking in the next 5 years ( p < 0.0001 ) as presented in table 2 . also , table 2 shows , 61.9% ( 787 ) of students had poor knowledge ; whereas , this rate was 38.8% ( 213 ) among clergymen and 42.1% ( 232 ) among teachers . inappropriate attitude ( tendency ) towards smoking was observed in 23.1% ( 294 ) of students , 10.2% ( 56 ) of clergymen and 12.7% ( 70 ) of teachers . in addition , 11.9% ( 151 ) of students , 5.8% ( 32 ) of clergymen and 7.3% ( 40 ) of teachers predicted that they will smoke cigarette in the next 5 years . it worth mentioning that the knowledge , attitude , and probability of smoking in the next 5 years of two groups of medical and non - medical students were not statistically significant ( p = 0.29 ; p = 0.28 ; p = 0.30 ; data not shown ) , respectively . this was the reason that we combined these two groups of the students for comparisons between 3 groups . knowledge , attitude and prediction of smoking in the next 5 years among male students , teachers and clergymen in tehran table 3 shows the odds ratio of smoking initiation in the understudy groups based on their level of knowledge , and attitude . odds ratio of smoking cigarette was not significant in students with poor knowledge ( or = 1.2 ; 95% ci : 0.9 - 1.6 ) . whereas , odds ratio of smoking cigarette in clergymen ( or = 3.1 ; 95% ci : 2.0 - 4.6 ) and teachers ( or = 2.7 ; 95% ci : 1.9 - 4.0 ) with poor knowledge was significantly higher than those with moderate or good level of knowledge . also , in all 3 groups , the odds ratio of smoking cigarette was higher among those with inappropriate attitude compared to those with appropriate attitude towards smoking . this chance was significantly more in clergymen than teachers and was the lowest amongst students ( p = 0.01 ; table 3 ) . likelihood of smoking in the next 5 years of male students , teachers and clergymen based on their knowledge and attitude in tehran in addition , when examining the effect of current smoking status on the likelihood of smoking cigarette in the next 5 years , the corresponding odds ratios for students , clergymen and teachers were 1.4 , ( 95% ci : 0.98 - 2.0 ) , 4.0 ( 95% ci : 1.9 - 8.2 ) and 2.9 ( 95% ci : 1.5 - 5.6 ) respectively , which were significantly different ( p = 0.0001 ) . the results of study of association between knowledge , attitude and prediction of smoking in the next 5 in three groups are presented in table 4 . as shown in this table , 25.9% ( 204 ) of students with poor level of knowledge had also inappropriate attitude towards smoking cigarette ; whereas , only 15% ( 32 ) of clergymen and 17.2% ( 40 ) of teachers with poor knowledge had this attitude ( p < 0.0001 ) . also , 7.8% ( 61 ) of students with poor knowledge predicted that they may smoke cigarette in the next 5 years , where these rates were 3.8% ( 8) and 4.3% ( 10 ) among clergymen and teachers , respectively ( p in addition , it was found that 20.4% ( 60 ) of students with inappropriate attitude predicted that they may smoke cigarette in the next 5 years however these were 28.6% ( 16 ) and 28.6% ( 20 ) in clergymen and teachers ( p = 0.008 ) . these finding revealed that although frequency of inappropriate attitude was higher among students , the chance of smoking in the next 5 years in this group was lower than clergymen and teachers . as it is stated the age rage of the students and clergymen were 18 to 25 years and of the teachers 20 to 29 years . when significant test was carried on grade ( as a representative of age ) of students and clergymen it was not significant ( p = 0.37 ) . also , given the rage of age ( 20 to 29 years ) , the mean age of teachers is not generally far from the other 2 groups to alter the findings . the results of this study showed that prevalence of smoking was higher among students ( 31.1% ) and teachers ( 27.2% ) in comparison with clergymen ( 21.0% ) and other males in general population ( 23.4% ) . although , the lowest consumption was seen among clergymen , it was not significantly lower than general population ( p = 0.40 ) . also , level of knowledge , attitude and prediction of smoking cigarette in the next 5 years were more favorable in teachers and clergymen . although , whenever the range of age extended or the females are enrolled the findings could be different . in general , limited studies have compared smoking status in different groups in a community , although there are many researches focusing on a specific group of people . they evaluated 280 medical students in isfahan university of medical sciences and found that prevalence of smoking was 34% among male students who were in last year of their training . another study conducted in saudi arabia showed a relatively similar prevalence of smoking among students of different majors . in this study , which was conducted on 202 medical and 300 non - medical students , they demonstrated that the rate of smoking was 27.8% and 39.5% among medical and non - medical students , respectively . frisch et al . in malaysia examined the pattern of smoking , level of knowledge and attitude of 146 medical and nursing students towards smoking and found that only 11% of male students and none of the female students smoked which is much lower than ours . the level of knowledge and attitude were significantly lower in students compared with other groups in our study . however , other studies conducted in different countries demonstrated that level of knowledge and attitude of medical students towards smoking were more appropriate . a study conducted in the united kingdom on 181 dental students showed that more than 90% of dental students had moderate or good knowledge and more than 80% had an appropriate attitude towards smoking pizzo et al . in a study aiming to examine prevalence of smoking among dental students and their knowledge and attitude towards quitting showed that of 220 students 65% of students had appropriate knowledge and 87% had appropriate attitude towards smoking cessation activities . although in their study , the level of knowledge and attitude of dental students were higher than our students , no significant difference was observed between prevalence of smoking . this indicates that appropriate knowledge and attitude alone can not result in a proper behavior and other confounding factors like socioeconomic and family issues should also be taken into account . , in the netherlands examined knowledge , attitude and rate of smoking in 3 groups of medical students ( 725 subjects ) , residents ( 126 subjects ) and psychology counselors ( 236 subjects ) and found that prevalence of smoking among medical students and residents was lower than the general population ; whereas , prevalence of smoking among counselors was not different from general population . they also found that counselors had poorer knowledge and more inappropriate attitude towards smoking compared to the other 2 groups . the results of glantz study on prevalence of smoking in comparison with general population were in contrast with ours , however he found similar association between knowledge , attitude and prevalence of smoking cigarette with our study . limited studies have been conducted on the smoking status among clergymen of other religions and those available have been mostly performed on buddhist monks . a study conducted on 318 buddhist monks in cambodia showed that 44% were smokers ; whereas , prevalence of smoking in cambodian general population was 65% . in addition , most monks had a poor knowledge about hazards of smoking but as the result of social stigma , prevalence of smoking among them was lower than the general population . another study conducted on buddhist monks in laos showed that prevalence of smoking among them was about 12% , which is much lower than the neighboring countries like cambodia . this study also demonstrated that lao monks had a good knowledge about hazards of smoking . the results of these 2 studies were in accord with those of ours demonstrating that islamic clergymen and buddhist monks both had a lower prevalence of smoking than general population and also had an appropriate level of knowledge in this respect . in general , the majority of studies performed on teachers only studied the prevalence of smoking . our study findings regarding high prevalence of smoking among teachers were in agreement with the findings of talay et al . , in turkey , and sorensen et al . in india . on the contrary , a study in bahrain on 1,140 teachers demonstrated that only 8.7% of bahraini teachers smoked , which was lower than their general population . they also reported that these teachers had acceptable level of knowledge about hazards of smoking . the results of this study revealed that clergymen and teachers with poor knowledge had lower chance for becoming a smoker . in all 3 groups , the odds ratio of smoking in those with inappropriate attitude was significantly different from those with appropriate attitude . however , this chance was not significantly different in clergymen than teachers . also , it was found that smoking status had no significant effect on the probability of smoking in the next 5 years among students . however , for clergymen and teachers , likelihood of smoking in the next 5 years among current smokers was significantly different from non - smokers . in a study on 5,112 teachers in malaysia it also showed that teachers attitude affected their smoking status , which is in concord with our study findings . another study conducted in bosnia on 273 physicians and nurses found a significant difference in their knowledge and attitude towards smoking . while , in each group , prevalence of smoking . also found a significant relationship between prevalence of smoking and level of knowledge and attitude in each group of medical students , psychologists and medical residents . preventing the initiation of smoking in the adolescents and decreasing the prevalence of smoking in adults are the most important methods for prevention of cancer and various diseases . these programs may include increased price of cigarettes , ban of smoking in public places , limiting cigarette advertisements , restricting tobacco advertising , and establishment of counseling and treatment centers for nicotine dependence . however , for implementation of such programs at the national level , a correct estimate of the prevalence of smoking in different social and occupational groups seems necessary . cigarette consumption has increased among the youth of various social levels in the recent years . this study also showed that prevalence of smoking was higher among male students ( which represents the youth in the community ) than general population . considering this increase , new strategies the strength of this study was looking at these 3 groups for the first time , having standard questionnaire , trained research staff and acceptable executive process . the weakness of the study was because the clergyman were male the other 2 groups were selected from males . also , limiting the information on grades of the students and clergymen and age rage of teachers and not recording exact age of participants was of the limitations of the study . this study showed that prevalence of smoking among male students and teachers was higher than general population and clergymen , who smoked equally . also , level of knowledge and attitude and prediction of future smoking in students were worse than teachers and clergymen , which is alarming .
background : students , clergymen and teachers as role models can be very important in encouragement or prevention of cigarette smoking in young people . the aim of this study was to compare prevalence of smoking in 3 male groups of teachers , clergymen and university students . also , study their knowledge and attitude towards it and the prediction of their future consumption.methods:in a cross sectional study in 2009 in tehran , iran , 1,271 male students , 549 clergymen and 551 teachers were randomly enrolled . 
 each participant completed the global adult tobacco survey questionnaire . 
 knowledge , attitude and prediction of smoking for the next 5 years were questioned in these 3 groups . 
 chi - squared test and logistic regression were used for analysis . 
 p < 0.05 was considered significant.results:prevalence of cigarette smoking was 31.1% , 21.9% and 27.2% among students , clergymen and teachers , respectively . smoking in students 
 was not associated with poor knowledge but were in teachers and clergymen . 
 the odds ratio of smoking in students , clergymen and teachers was higher among those with having inappropriate attitude towards it ( or = 1.6 , 6.1 and 4.5 ) . 
 those with poor knowledge had an inappropriate attitude and predicted higher chance of cigarette consumption in the next 5 years ( p < 0.0001 ) . 
 inappropriate attitude in all 3 groups resulted in higher prediction of future smoking ( p = 0.008).conclusions : this study revealed that the prevalence of smoking among male students and teachers was higher than general population and clergymen who equally smoked . 
 also , level of knowledge and attitude of students were lower than teachers and clergymen .