, many countries have made efforts to prevent and reduce tobacco use in this vulnerable age group ( 1 ) . to achieve this goal , factors that influence smoking in adolescents in different communities need to be understood .
a study in turkey showed that household size , higher birth rank , school type , low academic performance , exposure to second - hand smoke , and stress were important factors influencing tobacco use in high - school students ( 2 ) . in a brazilian study , the period of late adolescence , attending a private school , and work activities were associated with the initiation of hookah use ( 3 ) .
parental tobacco use was also reported to increase the risk of smoking initiation in adolescents ( 4 ) .
a study of canadian students showed that younger age , single - parent family status , stress , impulsivity , low self - esteem , experimentation with smoking , poor school performance , susceptibility to tobacco advertisements , alcohol use , consumption of other tobacco products , and attending a smoking - tolerant school , as well as smoking by parents , siblings , friends , and school staff , were the main determinants of smoking initiation ( 5 ) .
a community - based study in iran showed that older age , poor parental control of children , insufficient parental supervision of adolescents in friend selection , and having a smoker friend or family member were associated with lifetime cigarette use among male adolescents ( 6 ) .
a study in nepal demonstrated that late adolescence , male gender , attending a public school , and a substantial amount of pocket money were associated with tobacco use in secondary - school students ( 7 ) .
another study in nepal showed that substance use and parental smoking were associated with smoking among medical and dental students ( 8) . a study of middle - school students in the u.s .
underscored the independent role of seeing tobacco use in films in the initiation of smoking by adolescents ( 9 ) . in a study in iran , age , grade , the mother s job , and education had statistically significant differences between tobacco smokers and nonsmokers ( 10 ) .
although many common factors seem to influence tobacco use at a young age in different countries , understanding the determinants of using different kinds of tobacco in various populations is necessary to plan international and national preventive programs .
the current study aimed to assess the determinants of smoking tobacco and hookah use in a nationally representative sample of iranian students .
the data of this study were collected as a part of a national survey of school student high - risk behaviors ( 2011 - 2012 ) , as part of the fourth survey of a school - based surveillance system entitled childhood and adolescence surveillance and prevention of adult non - communicable disease ( caspian - iv ) study .
a total sample size of 480 subjects in each province was calculated as the maximum sample size needed to provide an optimal estimate of all the risk factors of interest . from the 30 provinces ,
48 clusters of 10 subjects were selected in each province , in addition to 14,880 students and an equal number of their parents . using the multistage , cluster - sampling method ,
the students were selected from urban and rural areas of different cities in the 30 provinces of the country ( 48 clusters of 10 students in each province ) .
stratification was done in each province according to the area of residence ( urban / rural ) and school grade ( elementary / intermediate / high school ) .
the sampling was proportional to the size , with an equal sex ratio ( i.e. , equal numbers of boys and girls were selected from each province , and the ratios in urban and rural areas were balanced to the population of urban and rural students ) . in this way
, the number of samples in the rural / urban areas and in each school grade was divided equally between the populations of students in each grade .
cluster sampling with equal clusters was used in each province to scope the required sample size .
the clusters were concluded the level of schools , including 10 sample units ( the students and their parents ) in each cluster .
the maximum sample size in each province required to provide a good estimate of all the risk factors of interest was calculated as 480 students . finally , 48 clusters of 10 subjects in each of the provinces ( n = 14,880 students ) were selected . with the participation of trained teams of expert health care providers , all processes of examinations and inquiry follow under standard protocols of the world health organization - global school - based student health survey ( 10 ) .
the validity and reliability of the questionnaire were confirmed in a previous study ( 12 ) . the cronbach s alpha and pearson s correlation coefficient for the reliability and stability of the questionnaire was 0.97 and 0.94 , respectively . in the cvi assessment ,
the questions were about demographic characteristics , parents education levels and occupations , students school grades , birth orders , family sizes , smoking habits , smoking habits of the families , school types ( public / private ) , living with parents , and exposure to tobacco smoke , as well as the time spent with friends , physical activity level , sleep duration , and screen time .
individuals who reported having tried smoking any tobacco product were considered ever smokers , and those who reported that they continued smoking at the study time were considered current smokers .
a hookah smoker was based on self - reports of hookah use at the time of the study .
approval for the study was obtained from the ethical committees of isfahan university of medical sciences , tehran university of medical sciences ( tums ) , and other relevant regulatory organizations at national and provincial levels . after explaining the study objectives and protocols , written consent and verbal assent were obtained from the parents and students , respectively .
the students were reassured about the confidentiality of their answers , and the questionnaires were completed anonymously .
continuous variables are reported as the mean and 95% confidence interval ( ci ) , and categorical variables are presented as a percentage ( 95% ci ) . the association of age with smoking was assessed using an independent sample t - test .
chi - square tests were used to compare the prevalence rates in the study groups .
multiple logistic regression ( mlr ) models using the enter method were fitted to assess the factors that increased or decreased the risk of smoking .
all variables having a p value of < 0.2 in the univariate analysis were included in the mlr model .
2011 , stata statistical software ( release 12 . college station , tx : stata corp lp .
the sample size in this nationwide study was calculated based on the cluster sampling method .
a total sample size of 480 subjects in each province was calculated as the maximum sample size needed to provide an optimal estimate of all the risk factors of interest . from the 30 provinces ,
48 clusters of 10 subjects were selected in each province , in addition to 14,880 students and an equal number of their parents . using the multistage , cluster - sampling method ,
the students were selected from urban and rural areas of different cities in the 30 provinces of the country ( 48 clusters of 10 students in each province ) .
stratification was done in each province according to the area of residence ( urban / rural ) and school grade ( elementary / intermediate / high school ) .
the sampling was proportional to the size , with an equal sex ratio ( i.e. , equal numbers of boys and girls were selected from each province , and the ratios in urban and rural areas were balanced to the population of urban and rural students ) . in this way
, the number of samples in the rural / urban areas and in each school grade was divided equally between the populations of students in each grade .
cluster sampling with equal clusters was used in each province to scope the required sample size .
the clusters were concluded the level of schools , including 10 sample units ( the students and their parents ) in each cluster .
the maximum sample size in each province required to provide a good estimate of all the risk factors of interest was calculated as 480 students .
finally , 48 clusters of 10 subjects in each of the provinces ( n = 14,880 students ) were selected .
with the participation of trained teams of expert health care providers , all processes of examinations and inquiry follow under standard protocols of the world health organization - global school - based student health survey ( 10 ) .
the validity and reliability of the questionnaire were confirmed in a previous study ( 12 ) . the cronbach s alpha and pearson s correlation coefficient for the reliability and stability of the questionnaire was 0.97 and 0.94 , respectively . in the cvi assessment ,
the questions were about demographic characteristics , parents education levels and occupations , students school grades , birth orders , family sizes , smoking habits , smoking habits of the families , school types ( public / private ) , living with parents , and exposure to tobacco smoke , as well as the time spent with friends , physical activity level , sleep duration , and screen time .
individuals who reported having tried smoking any tobacco product were considered ever smokers , and those who reported that they continued smoking at the study time were considered current smokers .
a hookah smoker was based on self - reports of hookah use at the time of the study .
approval for the study was obtained from the ethical committees of isfahan university of medical sciences , tehran university of medical sciences ( tums ) , and other relevant regulatory organizations at national and provincial levels . after explaining the study objectives and protocols , written consent and verbal assent were obtained from the parents and students , respectively .
the students were reassured about the confidentiality of their answers , and the questionnaires were completed anonymously .
continuous variables are reported as the mean and 95% confidence interval ( ci ) , and categorical variables are presented as a percentage ( 95% ci ) .
the association of age with smoking was assessed using an independent sample t - test .
chi - square tests were used to compare the prevalence rates in the study groups .
multiple logistic regression ( mlr ) models using the enter method were fitted to assess the factors that increased or decreased the risk of smoking .
all variables having a p value of < 0.2 in the univariate analysis were included in the mlr model .
2011 , stata statistical software ( release 12 . college station , tx : stata corp lp .
they were 6640 ( 49.2% ) girls and 6846 ( 50.8% ) boys , of whom 75.6% were from urban areas , and 24.4% were from rural areas .
the mean age of the participants was 12.47  3.36 years , with no significant difference between boys ( 12.36  3.40 years ) and girls ( 12.58  3.32 years ) ( p > 0.05 ) . according to the self - reports of the students , 2.6% ( 3.5% of boys and 1.7% of girls ) were current tobacco smokers , 5.9% ( 7.5% of boys and 4.2% of girls ) were ever tobacco smokers , and 1.8% ( 2.49% of boys and
table 1 shows the sociodemographic characteristic of the participants , according to their current or ever - smoking habits in the univariate analysis .
the mean ( 95% ci ) age of the current smokers ( 15.55 [ 15.28 , 15.82 ] vs. 12.39 [ 12.33 , 12.45 ] ) and ever smokers ( 15.14 [ 14.94 , 15.34 ] vs. 12.30 [ 12.25 , 12.36 ] ) was significantly higher than that of the never smokers .
the frequency of current tobacco use was significantly higher in boys than in girls ( 3.49% [ 95% ci : 2.91 , 4.18 ] vs. 1.66% [ 95% ci : 1.32 , 2.08 ] ) .
likewise , the frequency of ever tobacco use was significantly higher in boys ( 7.48% [ 95% ci : 6.54 , 8.54 ] vs. 4.19% [ 95% ci : 3.6 , 4.87 ] ) .
overall , 3.01% of the urban students and 1.28% of the rural students were current tobacco smokers .
the corresponding figures for ever tobacco use were 6.54% and 3.8% , respectively , with a significantly higher frequency in urban than rural residents ( p < 0.001 ) .
based on the mlr model ( table 2 ) , the following factors increased the risk of current tobacco smoking : age ( or = 1.37 [ 95% ci : 1.29 , 1.44 ] ) , time spent with friends ( 1 - 3 days ) ( or : 1.43 [ 95% ci : 1.07 , 1.91 ] ) , and > 3 days ( or:1.96 [ 95% ci : 1.38 , 2.79 ] ) , hookah smoking by the father ( or : 3.02 [ 2.15 , 4.25 ] ) , hookah smoking by sister(s ) or brother(s ) ( or : 4.01 [ 95% ci : 2.76 , 5.8 ] ) , hookah smoking by other members of the family ( or : 4.00 [ 95% ci : 2.82 , 5.67 ] ) , cigarette smoking by the father ( or : 1.63 [ 95% ci : 1.26 , 2.1 ] ) , and more than 2 hours / day screen time compared to less than 2 hours / day screen time ( or : 1.64 [ 95% ci : 1.26 , 2.14 ] ) .
female gender ( or : 0.51 [ 95% ci : 0.38 , 0.70 ] ) and living in a rural area ( or : 0.62 [ 95% ci : 0.40 , 0.97 ] ) decreased the risk of current smoking .
the association between the independent variables in the univariate model and hookah use are presented in table 3 . as shown , the mean age of the participants who smoked a hookah was significantly higher than those who did not ( 15.75 [ 95% ci : 15.47 , 16.03 ] vs. 12.39 [ 95% ci : 12.33 , 12.45 ] ) .
the frequency of hookah use was significantly higher among boys than girls ( 2.49% [ 95% ci : 2.02 , 3.08 ] vs. 1.14% [ 95% ci : 0.87 , 1.50 ] ) and among urban than rural students ( 2.14% [ 1.79 , 2.56 ] vs. 0.85% [ 0.55 , 1.32 ] ) .
the association between all the factors , except the mother s educational level , living with parents , family size , and physical activity , with hookah use was statistically significant in the univariate model . in the mlr model , age , the number of days spent with friends , hookah smoking or cigarette smoking by the father , hookah smoking by sister(s ) or brother(s ) , and screen time increased the risk of hookah smoking , and female gender and living in a rural area decreased the risk of hookah smoking in students ( table 4 ) .
this nationwide survey , which to the best of our knowledge is the first of its kind in the middle east and north africa region , showed that tobacco use is a health concern in iranian children and adolescents .
this finding is in line with previous studies in different countries ( 6 , 13 - 17 ) .
likewise , some previous studies in iran reported a higher frequency of current and ever smoking among boys than girls ( 6 , 15 , 16 , 18 - 20 ) .
the current study suggested that the presence of a smoker in the family , especially hookah use by a sister or brother , increased the risk of smoking in adolescents .
this finding is consistent with a previous nationwide iranian study , which showed that tobacco use at home , especially by a sister or brother , increased the likelihood of smoking in adolescents ( 13 ) .
another study in iran found that smoking by friends and family members was associated with smoking among medical students ( 20 ) .
many previous studies confirmed that tobacco use by parents and other relatives was a risk factor for intention to smoke in adolescents ( 21 - 25 ) . in the current study , spending more time with friends increased the risk of smoking in adolescents .
given the impact of friends on adolescent smoking , it seems that spending more time with friends increases the risk of smoking .
inadequate parental supervision of children may also explain the association between the time spent with friends and the increased risk of smoking .
some researchers documented that direct peer pressure was positively and independently associated with smoking and suggested that authoritative parents supervised and prevented their children associating with deviant peers , thereby preventing smoking in adolescence ( 21 , 22 ) .
some studies also suggested that peer smoking was associated with positive attitudes toward cigarettes smoking ( 23 ) and might increase the friendship with deviant peers and the risk of smoking ( 24 ) .
nonsmoker parents and strong family monitoring and bonding were reported to be associated with a lower risk of smoking initiation among children ( 25 ) .
another study reported statistically significant differences between tobacco smokers and nonsmokers according to age , grade , the mother s occupation , and education ( 10 ) .
a study of high - school boys documented a significant relationship between smoking behavior of best friends and the intention to smoke among peers ( 26 ) .
attachment to friends and having friends who smoked were common factors related to the onset of smoking in both male and female adolescents ( 27 ) .
in the present study , screen time of more than 2 h increased the risk of smoking 1.64 times in adolescents .
a study conducted in six european countries suggested a causal relationship between exposure to smoking in movies and smoking initiation in adolescents ( 28 ) .
in addition to this mechanism , we suggest that prolonged screen time and smoking can be considered two health risk behaviors as different aspects of an unhealthy lifestyle .
the present study showed that the prevalence of current hookah ( or kalian in the persian language ) use among adolescents was 2.49 ( 2.02 , 3.08 ) in boys and 1.14 % ( 0.87 , 1.5 ) in girls .
a report by iran gyts in 2007 found that 16.5% of students aged 13 - 15 years were current hookah users ( 30 ) .
a study of tunisians aged 13 - 17 years reported that 5.2% were current hookah users ( 31 ) .
other studies conducted in new jersey in the u.s . and beirut reported that 9.7% of high - school students ( 32 ) and 29.6% of secondary - school students were current hookah users ( 33 ) .
our findings suggested that the use of a hookah or cigarettes by family members was associated with hookah use in students .
this finding is in line with that of amok and colleagues who reported that the presence of a hookah user at home increased current hookah use by students ( 34 ) and the study by jamil et al . who reported that having a father , mother , or sibling who smoked a hookah at home was a significant risk factor for current hookah smoking ( 35 ) .
a study in iran demonstrated that having a hookah smoker in the family was associated with hookah use ( 36 ) .
rice and colleagues reported that having friends and family members who smoked were predictors of cigarette smoking and hookah use ( 37 ) .
in the current study , increased spent time with friends was associated with hookah use in adolescents .
a study of high - school student in san diego county showed that half of students first understand about hookah from friends ( 38 ) .
another study reported that 90.7% of students preferred to use a hookah with friends ( 3 ) .
in the current study , hookah use was more common among older students and male students .
many studies have demonstrated that hookah use increased with age ( 3 , 34 , 39 , 40 ) and that it was more common among males than females ( 41 ) .
however , in studies conducted by jamil et al . , male gender and younger age were associated with current hookah smoking ( 35 , 42 ) .
one of the main strengths of the present study is that it was based on a large national representative sample of iranian children and adolescents .
moreover , it adhered to the protocol of the world health organization s global school - based student health survey .
the main limitation of this study was its cross - sectional design and some limitation of recall bias of participants in some information .
considering the harmful effects of smoking , public health practitioners and health care providers should identify high - risk individuals and design educational programs to prevent the use of all kinds of tobacco products .
the preparation of strategies on the promotion of a healthy lifestyle through vast advocacy on the health impacts of tobacco smoking and access to appropriate health services as needed should be considered as the most priorities of youth health .
 backgroundthe consumption of tobacco through a hookah is growing in popularity , especially among children and adolescents , but little is known about the determinants of hookah smoking.objectivesthe current study aimed to assess the determinants of tobacco smoking and hookah smoking in a nationally representative sample of iranian children and adolescents.patients and methodsthis study was conducted as part of the fourth cross - sectional survey of a national school - based program . using a cluster random sampling method , a validated questionnaire was completed anonymously by 14,880 students who were aged 6 - 18 years and living in urban and rural areas of 30 provinces in iran.resultsthe final study group consisted of 13,486 children and adolescents ( participation rate of 90.6% ) , of whom 49.2% were girls and 75.6% were urban residents . 
 the mean age was 12.47  3.36 years . 
 according to the self - reports of the students , 2.6% ( 3.5% of boys and 1.7% of girls ) were current tobacco smokers , 5.9% ( 7.5% of boys and 4.2% of girls ) were ever tobacco smokers , and 1.8% ( 2.49% of boys and 1.14% of girls ) were current hookah smokers . 
 based on a multiple logistic regression ( mlr ) model , the following factors increased the risk of current smoking : age , number of days spent with friends per week , hookah smoking or cigarette smoking by the father , hookah smoking by siblings , hookah smoking by other members of the family , and screen time . 
 the age , number of days spent with friends , hookah or cigarette smoking by the father , hookah smoking by siblings , and screen time increased the risk of hookah smoking . 
 female gender and living in rural areas decreased the risk of current tobacco and hookah smoking.conclusionspreventive measures against tobacco use should be underscored for iranian families . 
 the preparation of strategies on the promotion of a healthy lifestyle should be considered a health priority . 
1. Background
2. Objectives
3. Patients and Methods
3.1. Study Population and Sampling Framework
3.2. Questionnaires
3.3. Ethical Concerns
3.4. Statistical Analysis
4. Results
5. Discussion