The relationship between marijuana smoking and asthma is somewhat complex

Water pipes have become more popular in North America in recent years due to the belief that it is a safer alternative to cigarettes .This is a common misconception in young adults,as a water pipe smoking session can contain over 100 times the amount of smoke in comparison to a single cigarette .In Ontario,the rate of trying water pipes in adolescents has more than doubled from 6% in 2006 to 14% in 2013.Water pipe smoking is linked to several adverse health outcomes such as cancer,cardiovascular disease and decreased lung function.While the causal effect of water pipe smoke and asthma has not been demonstrated,exposure to tobacco smoke was shown to exacerbate asthma symptoms.Since water pipes produce tobacco smoke,it can be assumed that it will be harmful especially for those with asthma.Marijuana has been used as a forbidden medicine to treat asthma symptoms for years as it may have bronchodilator properties,while long term marijuana smoking has also been associated with increased respiratory symptoms.Overall,the relationship between marijuana and lung health is somewhat mixed and the connection may not be the same as tobacco smoke.Previous research has suggested that adolescents with asthma smoked significantly more marijuana than those without asthma.However,the number of adolescents who smoked marijuana in Canada has decreased from 32.7% in 2008 to 24.4% in 2013.Electronic cigarettes are battery powered devices that vaporise nicotine and/or other flavouring mixes,cannabis grow lights but do not burn tobacco.These products have become popular in recent years and they are perceived as a safer alternative to tobacco cigarettes.

While preliminary studies suggest that they may be less harmful than cigarettes,the long term health effects and how e-cigarettes relate to asthma symptoms or severity are unknown.The Canadian Tobacco,Alcohol and Drug Survey reported that as many as one in five adolescents aged 15e19 tried e-cigarettes,however,the absolute trend of usage is still unknown as these products are relatively new.The purpose of this paper is to examine whether adolescents with asthma smoke cigarettes,water pipes,marijuana or e-cigarettes more or less than those without asthma.This study adds to the current literature by examining all smoking habits for youth with asthma,rather than focusing just on cigarettes.The 2013 Ontario Student Drug Use and Health Survey is a population based survey conducted every two years and completed by grade 7e12 students at publically funded schools in Ontario,Canada.Ontario is the largest province in Canada with a population of over 13 million residents.Ontario includes major urban centres such as Toronto and Ottawa,several smaller cities and an abundance of rural lands.The OSDUHS is designed to collect information about drug use and other health related behaviours among students in Ontario.All parents and students gave consent prior to participation.To examine the association between smoking and asthma,we limit our study sample to high school students in 109 schools.These schools were selected with probability proportional to size,to obtain a representative sample within the province.The survey included questions that captured information on self-reported doctor diagnosed asthma and data on tobacco,alcohol and drug use.The survey used a random split-ballot design where some of the questions change on each of the surveys.The sample is randomly divided into 2 groups to maximize questions included and minimize burden on students,but it reduces the sample size for some questions.In the OSDUHS,approximately half of the full sample answered questions pertaining to asthma and all types of smoking reducing the sub-sample to 2,840.

Data are representative of students in Grades 9 to 12 attending publicly funded schools in Ontario.Ages for respondents range from 12 to 19 years of age.In Ontario,the majority of children attended publically funded schools,5% attended private schools,and another 3% were either home schooled,institutionalized for correctional or health reasons,schooled on a First Nation reserve,military base or lived in remote northern region.This study was approved by the research ethics board at the Research Institute of The Hospital for Sick Children.The primary outcome variables in this study are smoking status with regard to cigarettes,water pipes,marijuana and e-cigarettes.Self-reported frequency and intensity of cigarette,water pipe,marijuana and e-cigarette smoking in the last 12 months and lifetime use were measured in the survey.Cigarette non-smokers were classified as those who never smoked a cigarette or smoked less than one cigarette in the last 12 months,while cigarette smokers were those who smoked more than one cigarette in the past 12 months.Similarly,smoking status for water pipe was also classified as a binary outcome variable.Respondents were asked how often they smoked a water pipe in the last 12 months.Those who smoked a few puffs,never smoked,haven’t smoked in the past 12 months or didn’t even know what it was were considered non-water pipe smokers.Those who smoked one or more times were defined as smokers.Marijuana smoking is also defined in a similar manner.Students were asked how often they smoked cannabis in the past 12 months.If they smoked 1 or more times in the past year they were classified as a marijuana smoker.Respondents who have never or not smoked in the last 12 months were considered to be non-marijuana smokers.Finally,respondents were classified as e-cigarette smokers if they smoked an e-cigarette with or without nicotine in it,while those who have never smoked or never heard of e-cigarettes were considered non-smokers.The primary risk factor of interest is the presence of asthma which is captured by the response to the question “has a doctor or nurse ever told you that you have asthma”.Other potential confounding variables include: grade,sex and socioeconomic status.

SES was measured by a 10-point social ladder.Students were asked to imagine that the ladder represents how Canadian society is set up,where the people at the top of the ladder are the “best off”,meaning they have the best jobs,make the most money and have the highest education.Those at the bottom of the ladder are the “worst off”,with no job,or a job no one wants,little education and the least money.Respondents reported what best represents their family on a 10-point scale,which was further grouped into three levels based on the interquartile ranges.The percent distributions of demographic characteristics and other co-variates were compared between smokers and nonsmokers of each type and the any smoking variable.The chi-square test was used to measure statistical significance between the respondents with and without asthma.Each type of smoking was modelled separately using a binary logistic regression.In addition to doctor diagnosed asthma,all co-variates outlined above were included in the regression models.All interactions of smoking types were examined but no significant relationships were found so this study focussed on the four individual models,plus the combined any smoking outcome.The following was used as the reference group in the logistic regression models: grade 9,female and high SES.Given the OSDUHS used a probability stratified cluster sampling design,all analyses were conducted with the sampling weights and utilized Taylor series methods within Stata 14 v14.1 to derive unbiased standard errors and point estimates.Results of the regression models were presented in adjusted odds ratios with 95% confidence intervals.Goodness of fit tests were completed with the F-adjusted mean test.While cigarette smoking may aggravate symptoms and severity for adolescents with asthma,some work on the topic suggests that the prevalence of cigarette,water pipe and marijuana smoking was actually higher in adolescents with asthma than those without.These studies,however,are not conclusive as at least one reported that adolescents with asthma were less likely to smoke cigarettes.It is reasonable to suppose that adolescents with asthma will not smoke as it will aggravate their asthma severity and symptoms,but this unfortunately may not be the case.

Our study showed that students in grades 9e12 with asthma in Ontario,had a higher odds of smoking e-cigarettes or any substance than their peers who do not have asthma.The odds of smoking ecigarettes for adolescents with asthma,was nearly twice as high as those without asthma after adjusting for age,sex and SES.Given the cross-sectional design of the survey,we cannot infer the causal relationship between smoking and asthma.Previous studies suggest that smoking for adolescents with asthma may relate to the desire to obtain social status among one’s peers,and not wanting asthma to interfere with their social status.Of all demographic characteristics studied,student’s grade was most significantly associated with smoking cigarettes,water pipes and marijuana.A longitudinal study in the United States found that rates of cigarette smoking increased from 1.8% at the age of 9 to 22.5% by age 16.Findings suggest that rates for smoking cigarettes and water pipes among grade 9 students were relatively low,but doubled in grade 10,tripled by grade 11 and quadrupled by grade 12.Cigarette and water pipe smoking became more popular in grade 10 and the trend continued as they aged.E-cigarette smoking on the other hand only marginally increased from grade 9 to 12.For adolescents with asthma,rates of e-cigarette smoking were similar to that of the entire sample,cannabis grow tent ranging from about 10% in grade 9 to 16.7% in grade 12.Our study also showed that cigarette,marijuana and any smoking rates were inversely related to SES,where lower SES was associated with higher odds of smoking.Our finding is consistent with the literature that suggests an inverse relationship between individual SES or parental education and cigarette smoking in adolescents.It has been suggested that lower SES households may have a poorer attitude towards health,fewer opportunities or more stressful situations which make them more likely to smoke.Results from our study emphasise the need for tailored interventions for youth from lower SES households.This study had many strengths which relate to the size and generalizability of the survey sample and the fact that it examined how all types of smoking related to asthma prevalence.That being said,there are also some limitations.The primary purpose of this survey is to examine health risk behaviours of adolescents in Ontario and not asthma.As such,the number of respondents with asthma was low and this may have contributed to some of the insignificant findings.

Despite the low number of asthma respondents,the self-reported asthma prevalence rate of adolescents in this study was similar to that reported by the Ontario Asthma Surveillance Information System,which uses a validated health administrative data case definition to capture asthma with 84% sensitivity and 76% specificity.Secondly,the cross-sectional design of the survey is a major study limitation in assessing causal relation of asthma and smoking.It is unknown from this study whether adolescents with asthma smoked e-cigarettes more often or if smoking e-cigarettes contributed to the risk of asthma.Thirdly,asthma was self-reported and it not clinically confirmed.Self-reported asthma may over or under represent actual prevalence of asthma.Furthermore,many studies that examined the relationship between asthma and smoking did not separate severe or “uncontrolled” asthma from those with well-controlled mild to moderate asthma.The effect of smoking on adolescents with severe or uncontrollable asthma may be different than on those with mild to moderate asthma.The definition of smoking used may influence the study findings.We classified smoking for cigarettes,marijuana and water pipes as smoking one or more time over the past 12 months or ever for e-cigarettes.This definition includes those who smoke regularly but also adolescents who experiment with the various types of smoking.This classification of smoking has been used previously in studies using the OSDUHS dataset.We conducted additional analyses using another method of classifying smokers reported by Wong and colleagues.In this method a regular smoker is defined as smoking more than 100 cigarettes in their lifetime and any cigarettes in the past month.Using this method the results and point estimates remained very similar.Given this method of classification was only available for cigarettes,we opted to retain the ‘any cigarettes over the past 12 months’ method to ensure measurement correspondence with the other types of smoking.Nevertheless,results suggest that adolescents with asthma are at least experimenting with e-cigarettes or any type of smoking more often than their peers without asthma,which may lead to higher smoking rates later in life.Finally,we were unable to adjust for parental smoking or parental history of asthma as these data were not collected by the survey.Having a parent who smokes may relate to the respiratory health of children,but it also increases the odds of smoking for adolescents.While information on parental smoking is not available in our data,further research should examine the association between parental smoking and asthma for all types of smoking.This paper adds discussion to the question of whether adolescents with asthma would be less likely to smoke cigarettes,water pipes,marijuana or e-cigarettes.