Differential Effects of Cannabis and Tobacco on Lung Function in Mid-Adult Life

Association between oxidative balance score and lung function and FeNO and mortality in the US population

BACKGROUND

The Oxidative Balance Score (OBS) is a new indicator of overall antioxidant/oxidant balance that provides a comprehensive picture of the body's overall oxidative stress status, with higher OBS indicating greater antioxidant exposure. A limited number of studies have examined the association between OBS and lung function and FeNO, and we aimed to investigate the possible relationship between OBS and lung function and FeNO.

METHODS

Data utilized in this study were sourced from the 2007-2012 NHANES. Multivariable logistic regression was employed to investigate the association between OBS/lifestyle OBS (lifestyle antioxidants such as physical activity, etc., and lifestyle pro-oxidants such as alcohol, smoking, etc.)/dietary OBS (dietary antioxidants such as fiber, β-carotene, riboflavin, etc., and dietary pro-oxidants, such as total fat, etc.) and FEV1, FVC, PEF, FEF 25%- 75%, FeNO, as well as obstructive ventilation dysfunction. The dose-response association between the OBS and FEV1, FVC and PEF was explored using RCS analysis. Subgroup analysis and interaction tests were also conducted. We also used multivariable Cox regression modeling to explore the between OBS/lifestyle OBS/dietary OBS and all-cause and respiratory-related mortality.

RESULTS

A total of 8,568 participants were enrolled. A statistically significant association was observed between OBS/lifestyle OBS/dietary OBS and FEV1, FVC, and PEF levels. There was no statistical association between OBS, lifestyle OBS, dietary OBS, and FeNO levels. RCS revealed a linear relationship between OBS and both FEV1 and FVC levels. Notably, the positive correlation between OBS and dietary OBS with FEV1 was more significant in male participants. Conversely, the relationship between OBS and FVC levels was influenced by gender and BMI. The effects of the overall OBS, lifestyle OBS, and dietary OBS on lung function parameters were independent of whether participants had restrictive ventilatory dysfunction or obstructive ventilatory dysfunction.In addition, both the overall OBS and dietary OBS demonstrated significant inverse associations with all-cause mortality, whereas no statistically significant relationships were observed between these scores and respiratory-related mortality. Notably, only lifestyle OBS exhibited a significant inverse association with respiratory-related mortality.

CONCLUSION

In this study, OBS, lifestyle OBS, and dietary OBS levels were positively correlated with lung function parameters (FEV1, FVC and PEF) in U.S. adults. Exploring this association can enhance our understanding of how oxidative homeostasis influences lung function changes. This could provide valuable interventions for lung function decline. We also found that higher OBS was associated with lower all-cause mortality. Adopting a healthy lifestyle and consuming an antioxidant-rich diet may significantly improve the prognosis of patients by reducing oxidative stress-related damage.

DNA methylation and gene expression of immune cell markers in adolescents with chronic cannabis use: an exploratory study

BACKGROUND

Experimental studies indicate that phytocannabinoids have immune-modulatory properties. However, the effects of chronic cannabis use (CCU) in adolescents on their immune cells have been scarcely investigated to date, although CCU is increasingly observed in this age group.

METHODS

In this study, we analyzed DNA methylation and gene expression of immune cell markers in whole-blood samples of adolescent CCU-outpatients and non-cannabis-using (NCU) controls (n = 14 vs. n = 15, mean age = 16.1 ± 1.3 years). Site-specific DNA methylation values were used to calculate A) proportion estimates of circulating white blood cell (WBC) types and B) mean DNA methylation values of common immune cell markers (CD4, CD8A, CD19, FCGR3A, CD14, FUT4, MPO), whose gene expression levels were additionally determined.

RESULTS

CCU adolescents had a lower estimated proportion of B cells compared to NCU subjects. An originally observed higher proportion of granulocytes in CCU subjects, however, was attenuated when controlling for past-year tobacco use. The observed differences in mean DNA methylation and gene expression of immune cell markers were not statistically significant.

CONCLUSION

The results of our explorative study indicate that CCU in adolescents is associated with altered levels of circulating WBCs. Further studies with larger cohorts are warranted to confirm our findings and to provide insights regarding their functional consequences.

Impact of Marijuana Use on Lung Health

The widespread use of marijuana in the context of increasing legalization has both short- and long-term health implications. Although various modes of marijuana use-smoked, vaped, or ingested-may lead to a wide scope of potential systemic effects, we focus here on inhalational use of marijuana as the most common mode with the lung as the organ that is most directly exposed to its effects. Smoked marijuana has been associated with symptoms of chronic bronchitis and histopathologic changes in airway epithelium, but without consistent evidence of long-term decline in pulmonary function. Its role in immunomodulation, both for risk of infection and protection against a hyperinflammatory host response to infection, has been suggested in animal models and in vitro without conclusive extrapolation to humans. Marijuana smoke contains carcinogens like those found in tobacco, raising concern about its role in lung cancer, but evidence is mixed and made challenging by concurrent tobacco use. Vaping may offer a potential degree of harm reduction when compared with smoking marijuana with reduction of exposure to several toxins, including carbon monoxide, and reduction in chronic respiratory symptoms. However, these potential benefits are counterbalanced by risks including vaping-associated lung injury, potentially more intense drug exposure, and other yet not well-understood toxicities. As more states legalize marijuana and the federal government considers changing this from a Schedule I to a Schedule III controlled substance, we anticipate an increase in prospective medical studies concerning the risks related to marijuana use. This review is based on currently available data concerning the impact of inhaled marijuana on lung health.

Distinct trajectories of lung function from childhood to mid-adulthood

RATIONALE

Life course trajectories of lung function development and decline influence the risk for lung disease but are poorly documented.

OBJECTIVE

To document lung function trajectories from childhood to mid-adult life.

METHODS

We modelled forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC at ages 9, 11, 13, 15, 18, 21, 26, 32, 38 and 45 years from a population-based cohort using latent profile analysis to identify distinct subgroups of participants with similar lung function trajectories. Regression analyses were used to assess associations between the trajectories, early life factors and postbronchodilator airflow obstruction at age 45.

RESULTS

Among 865 participants with ≥6 measures of lung function, we identified 10 distinct FEV1 trajectories. Most were approximately parallel except for a childhood airway hyper-responsiveness-related persistently low trajectory (3% of study population); two accelerated-decline trajectories, one of which (8%) was associated with smoking and higher adult body mass index (BMI) and a catch-up trajectory (8%). Findings for FEV1/FVC trajectories were similar. Nine trajectories were identified for FVC: most were also approximately parallel except for a higher BMI-related accelerated-decline trajectory. The three FEV1 trajectories leading to the lowest FEV1 values comprised 19% of the cohort but contributed 55% of airflow obstruction at age 45.

CONCLUSIONS

Lung function trajectories to mid-adult life are largely established before adolescence, with a few exceptions: a childhood airway hyper-responsiveness-related persistently low trajectory, which starts low and gets worse with age, and accelerated adult decline trajectories associated with smoking and obesity. Adverse trajectories are associated with a high risk of airflow obstruction in mid-adult life.

The Puzzle of Marijuana Use and Forced Vital Capacity

In study after study, marijuana use has been found to be associated with increased forced vital capacity (FVC). This is puzzling, because marijuana is commonly consumed by inhalation of its smoke, and smoke exposure of any kind is not generally considered a cause of increased FVC. Although this observation was first made decades ago, a satisfactory explanation remains elusive. In this review we survey the evidence supporting the relationship between marijuana use and increased FVC, discuss potential threats to validity when inferring causation, and, presupposing a possible causal relationship, pose two key questions. First, what are possible physiologic or pathophysiologic mechanisms by which marijuana use might increase FVC? Second, why might this effect be consistently observed with marijuana use but not with tobacco use? Explanations for the first question include lung and chest growth and remodeling from strenuous marijuana smoke inhalation and reductions in lung elastic recoil from marijuana smoke exposure. Explanations for the second include differences between marijuana and tobacco in smoke composition and patterns of consumption, such as smoking topography. Finally, the possibility that smoke, whether from marijuana or tobacco, might have nonmonotonic effects on FVC depending on the degree of exposure is explored. In synthesizing a curated breadth of epidemiologic and physiologic science, we leverage a perplexing observation to generate potential insights and avenues for further research into the biological effects of smoke, from marijuana or otherwise, on the respiratory system.

Cannabis Use Disorder Trends and Health Care Utilization After Cervical and Lumbar Spine Fusions

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To identify differences in complication rates after cervical and lumbar fusion over the first postoperative year between those with and without cannabis use disorder (CUD) and to assess how CUD affects opioid prescription patterns.

SUMMARY OF BACKGROUND DATA

Cannabis is legal for medical purposes in 36 states and for recreational use in 18 states. Cannabis has multisystem effects and may contribute to transient vasoconstrictive, prothrombotic, and inflammatory effects.

METHODS

The IBM MarketScan Database (2009-2019) was used to identify patients who underwent cervical or lumbar fusions, with or without CUD. Exact match hospitalization and postdischarge outcomes were analyzed at index, six, and 12 months.

RESULTS

Of 72,024 cervical fusion (2.0% with CUD) and 105,612 lumbar fusion patients (1.5% with CUD), individuals with CUD were more likely to be young males with higher Elixhauser index. The cervical CUD group had increased neurological complications (3% vs. 2%) and sepsis (1% vs. 0%) during the index hospitalization and neurological (7% vs. 5%) and wound complications (5% vs. 3%) at 12 months. The lumbar CUD group had increased wound (8% vs. 5%) and myocardial infarction (MI) (2% vs. 1%) complications at six months and at 12 months. For those with cervical myelopathy, increased risk of pulmonary complications was observed with CUD at index hospitalization and 12-month follow-up. For those with lumbar stenosis, cardiac complications and MI were associated with CUD at index hospitalization and 12 months. CUD was associated with opiate use disorder, decreasing postoperatively.

CONCLUSIONS

No differences in reoperation rates were observed for CUD groups undergoing cervical or lumbar fusion. CUD was associated with an increased risk of stroke for the cervical fusion cohort and cardiac (including MI) and pulmonary complications for lumbar fusion at index hospitalization and six and 12 months postoperatively. Opiate use disorder and decreased opiate dependence after surgery also correlated with CUD.

Lung function and cardiovascular risk at age 45 in a cohort of the general population

BACKGROUND

Impaired lung function is associated with cardiovascular mortality, but the origins of this association are poorly understood. We investigated associations between lung function and cardiovascular risk scores in a general population cohort of men and women aged 45 years.

METHODS

Participants are members of an unselected birth cohort followed to adulthood. Lung function determined at ages 32 and 45 by spirometry, body plethysmography, gas diffusion, and airway conductance were the main predictors. Future cardiovascular risk was estimated at age 45 using a multivariable cardiovascular risk algorithm - PREDICT. Risk scores were log-transformed and used as the dependent variable in linear regression analyses. We investigated cross-sectional associations with lung function at age 45 and longitudinal associations using changes in lung function between ages 32-45 as the predictors.

RESULTS

863 of 1037 original cohort participants had data for analysis. Low lung volumes (FEV1, FVC, VA, TLC, and FRC) were associated with greater cardiovascular risk scores in the cross-sectional analyses at age 45 and the longitudinal analyses. These associations were stronger in women than in men, were independent of smoking history, and present in never smokers, even after adjusting for body mass index. Associations were not found for measures of airway function (FEV1/FVC ratio and sGaw) or gas transfer (TLco/VA).

CONCLUSIONS

Low lung volumes at age 45 and accelerated pulmonary function decline are associated with a higher estimated cardiovascular risk scores in mid-adulthood. This association is stronger in women and is not explained by smoking or obesity.

Cannabis use and the prevalence of current asthma among adolescents and adults in the United States

OBJECTIVES

Cannabis use has increased among adolescents and adults in the United States (US) in recent years. Few data are available on the prevalence of asthma by frequency of cannabis use. This study aimed to estimate the prevalence of asthma by frequency of past 30-day cannabis use among US individuals.

METHODS

Data were drawn from the 2020 National Survey on Drug Use and Health (NSDUH), a nationally representative, annual cross-sectional survey of US individuals aged 12 and older in the United States (N = 32,893). Logistic regression models were used to examine the relationship between frequency of any cannabis and/or blunt (i.e., cannabis smoked in a hollowed-out cigar) use in the past 30 days and current asthma, adjusting for demographics and current cigarette smoking.

RESULTS

Current asthma was more common among US individuals who reported cannabis use in the past 30-days, relative to those who did not (9.8% vs. 7.4%, p < 0.0001). The odds of asthma was significantly greater among individuals reporting cannabis use 20-30 days/month (Adjusted Odds Ratio [AOR] = 1.67, 95% CI:1.21, 2.31), blunt use 6-15 and 20-30 days/month (AOR = 1.9, 95% CI:1.1, 3.2; AOR = 2.2, 95% CI:1.4, 3.6), respectively, than among those without. A positive linear relationship was observed between frequency of a) cannabis use (p < 0.0001) and b) blunt use (p < 0.0001) and current asthma prevalence.

CONCLUSIONS

Findings suggest a dose-response relationship between frequency of current cannabis use and the prevalence of current asthma in the US individuals.

Effects of cannabis smoking on the respiratory system: A state-of-the-art review

The diminished perception of the health risks associated with the consumption of cannabis (marijuana) lead to a progressive increase in its inhalational use in many countries. Cannabis can be smoked through the use of joints, spliffs and blunts, and it can be vaporised with the use of hookah or e-cigarettes. Delta-9 tetrahydrocannabinol (THC) is the main psychoactive component of cannabis smoke but contains numerous other substances. While the recreational use of cannabis smoking has been legalised in several countries, its health consequences have been underestimated and undervalued. The purpose of this review is to critically review the impact of cannabis smoke on the respiratory system. Cannabis smoke irritates the bronchial tree and is strongly associated with symptoms of chronic bronchitis, with histological signs of airway inflammation and remodelling. Altered fungicidal and antibacterial activity of alveolar macrophages, with greater susceptibility to respiratory infections, is also reported. The association with invasive pulmonary aspergillosis in immunocompromised subjects is particularly concerning. Although cannabis has been shown to produce a rapid bronchodilator effect, its chronic use is associated with poor control of asthma by numerous studies. Cannabis smoking also represents a risk factor for the development of bullous lung disease, spontaneous pneumothorax and hypersensitivity pneumonitis. On the other hand, no association with the development of chronic obstructive pulmonary disease was found. Finally, a growing number of studies report an independent association of cannabis smoking with the development of lung cancer. In conclusion, unequivocal evidence established that cannabis smoking is harmful to the respiratory system. Cannabis smoking has a wide range of negative effects on respiratory symptoms in both healthy subjects and patients with chronic lung disease. Given that the most common and cheapest way of assumption of cannabis is by smoking, healthcare providers should be prepared to provide counselling on cannabis smoking cessation and inform the public and decision-makers.

Case Report: Catastrophic Effects of Using Cannabis Via Bucket Bong in Top End Northern Territory of Australia

The prevalence of cannabis usage is increasing worldwide, including among both Indigenous and non-Indigenous Australians. The long-term effects of cannabis use on the lungs are well-known. However, the acute adverse effects on the lungs are sparsely reported. There are different ways in which cannabis can be inhaled, such as smoking or through a water vaporizing method known as a "bong." An improvised innovative bong device that is commonly used in Northern Australia, called a "bucket bong," uses water and air pressure to assist in cannabis inhalation. In this report, we describe three patients from remote and rural Northern Australian communities presenting with near-life-threatening events (acute pneumonitis and massive pneumothorax) immediately after the use of cannabis via bucket bong.

Impact of Marijuana Smoking on COPD Progression in a Cohort of Middle-Aged and Older Persons

Background

Limited data are available regarding marijuana smoking's impact on the development or progression of chronic obstructive pulmonary disease (COPD) in middle-aged or older adults with a variable history of tobacco cigarette smoking.

Methods

We divided ever-tobacco smoking participants in the SubPopulations and InteRmediate Outcomes In COPD Study (SPIROMICS) into 3 groups based on self-reported marijuana use: current, former, or never marijuana smokers (CMSs, FMSs or NMSs, respectively). Longitudinal data were analyzed in participants with ≥2 visits over a period of ≥52 weeks.

Measurements

We compared CMSs, FMSs, and NMSs, and those with varying amounts of lifetime marijuana use. Mixed effects linear regression models were used to analyze changes in spirometry, symptoms, health status, and radiographic metrics; zero-inflated negative binomial models were used for exacerbation rates. All models were adjusted for age, sex, race, baseline tobacco smoking amount, and forced expiratory volume in 1 second (FEV1) %predicted.

Results

Most participants were followed for ≥4 years. Annual rates of change in FEV1, incident COPD, respiratory symptoms, health status, radiographic extent of emphysema or air trapping, and total or severe exacerbations were not different between CMSs or FMSs versus NMSs or between those with any lifetime amount of marijuana use versus NMSs.

Conclusions

Among SPIROMICS participants with or without COPD, neither former nor current marijuana smoking of any lifetime amount was associated with evidence of COPD progression or its development. Because of our study's limitations, these findings underscore the need for further studies to better understand longer-term effects of marijuana smoking in COPD.

Do tobacco and cannabis use and co-use predict lung function: A longitudinal study

BACKGROUND

Use of tobacco and cannabis is common and has been reported to predict lung function. Less is known about co-use of tobacco and cannabis and their impact on changes in lung function to early adulthood.

RESEARCH QUESTION

The study examines whether cigarette smoking or cannabis use and co-use are each associated with lung function in a population sample of young adults.

STUDY DESIGN AND METHODS

Data are from a prospective cohort study of cigarette smoking, cannabis use and co-use at 21 and 30 years of age and lung function (FVC, FEV1, FEV1/FVC) measured at 30 years. Lung function results are transformed using Global Lung Function Formulae. Subjects are the children of pregnant women who were recruited into the cohort study over the period 1981-3. Respondents were administered a spirometry assessment at 21 and 30 years of age. These respondents completed a smoking and cannabis use questionnaire at 21- and 30-year follow-ups.

RESULTS

Cigarette smoking (with or without cannabis use) is associated with reduced airflow. There is no consistent association between cannabis use and measures of lung function. The co-use of tobacco and cannabis appears to entail no additional risk to lung function beyond the risks associated with tobacco use alone.

INTERPRETATION

Persistent cigarette smoking is associated with reduced airflow even in young adults. Cannabis use does not appear to be related to lung function even after years of use.

ASRA Pain Medicine consensus guidelines on the management of the perioperative patient on cannabis and cannabinoids

BACKGROUND

The past two decades have seen an increase in cannabis use due to both regulatory changes and an interest in potential therapeutic effects of the substance, yet many aspects of the substance and their health implications remain controversial or unclear.

METHODS

In November 2020, the American Society of Regional Anesthesia and Pain Medicine charged the Cannabis Working Group to develop guidelines for the perioperative use of cannabis. The Perioperative Use of Cannabis and Cannabinoids Guidelines Committee was charged with drafting responses to the nine key questions using a modified Delphi method with the overall goal of producing a document focused on the safe management of surgical patients using cannabinoids. A consensus recommendation required ≥75% agreement.

RESULTS

Nine questions were selected, with 100% consensus achieved on third-round voting. Topics addressed included perioperative screening, postponement of elective surgery, concomitant use of opioid and cannabis perioperatively, implications for parturients, adjustment in anesthetic and analgesics intraoperatively, postoperative monitoring, cannabis use disorder, and postoperative concerns. Surgical patients using cannabinoids are at potential increased risk for negative perioperative outcomes.

CONCLUSIONS

Specific clinical recommendations for perioperative management of cannabis and cannabinoids were successfully created.

The endocannabinoid system and breathing

Recent changes in cannabis accessibility have provided adjunct therapies for patients across numerous disease states and highlights the urgency in understanding how cannabinoids and the endocannabinoid (EC) system interact with other physiological structures. The EC system plays a critical and modulatory role in respiratory homeostasis and pulmonary functionality. Respiratory control begins in the brainstem without peripheral input, and coordinates the preBötzinger complex, a component of the ventral respiratory group that interacts with the dorsal respiratory group to synchronize burstlet activity and drive inspiration. An additional rhythm generator: the retrotrapezoid nucleus/parafacial respiratory group drives active expiration during conditions of exercise or high CO₂. Combined with the feedback information from the periphery: through chemo- and baroreceptors including the carotid bodies, the cranial nerves, stretch of the diaphragm and intercostal muscles, lung tissue, and immune cells, and the cranial nerves, our respiratory system can fine tune motor outputs that ensure we have the oxygen necessary to survive and can expel the CO₂ waste we produce, and every aspect of this process can be influenced by the EC system. The expansion in cannabis access and potential therapeutic benefits, it is essential that investigations continue to uncover the underpinnings and mechanistic workings of the EC system. It is imperative to understand the impact cannabis, and exogenous cannabinoids have on these physiological systems, and how some of these compounds can mitigate respiratory depression when combined with opioids or other medicinal therapies. This review highlights the respiratory system from the perspective of central versus peripheral respiratory functionality and how these behaviors can be influenced by the EC system. This review will summarize the literature available on organic and synthetic cannabinoids in breathing and how that has shaped our understanding of the role of the EC system in respiratory homeostasis. Finally, we look at some potential future therapeutic applications the EC system has to offer for the treatment of respiratory diseases and a possible role in expanding the safety profile of opioid therapies while preventing future opioid overdose fatalities that result from respiratory arrest or persistent apnea.

Cannabis - a Rewritten History and Its Pulmonary Consequences

Cannabis presents itself as another challenge of the last decade. Better and better deciphered through in-depth studies, this drug remains a source of scientific debates. Legalized in some states, it competes with tobacco regarding the effects generating respiratory symptoms, chronic bronchitis, bronchial cancer, respiratory infections, etc. In this article we will review the pharmacology, epidemiology, clinical and prevention aspects and try to demonstrate which of these are the most effective means of prevention. This review proves once again that this drug has many hidden dangers.

Marijuana and the Lung: Evolving Understandings

Human beings have used marijuana products for centuries. Relatively recent data showing extensive cannabinoid receptors, particularly in the brain, help to explain the impacts of cannabinoids on symptoms/diseases, such as pain and seizures, with major nervous system components. Marijuana can cause bronchitis, but a moderate body of literature suggests that distal airway/parenchymal lung disease does not occur; marijuana does not cause chronic obstructive pulmonary disease and probably does not cause lung cancer, distinctly different from tobacco. Potentials for cognitive impairment and for damage to the developing brain are contextually important as its beneficial uses are explored.

[Inhaled marijuana and the lung, a toxic cocktail?]

Unlike the well-documented effects of tobacco smoke on the lung, the effects of cannabis smoke remain controversial, the main bias consisting in co-consumption of tobacco. That said, the composition of joint smoke is close to that of cigarettes, containing many compounds that are carcinogenic and/or alter the respiratory epithelium. Confirmed respiratory effects in chronic cannabis smokers include aggravated chronic bronchitis symptoms, a cumulative effect with tobacco on COPD and emphysema occurrence, an increased risk of bullous emphysema, and pneumothorax with heightened risk of recurrence after pleural symphysis. Recent prospective studies have shown a negative impact on lung function, with not only damage to the airways, but also DLCO alteration and an accelerated drop in FEV1. Finally, cannabis smoking is very common among young patients with lung cancer. Its consumption could lead to a different lung cancer profile, potentially more undifferentiated and less accessible to targeted therapy. Questioning about cannabis consumption must be systematic and targeted medical care should be offered.

The Dunedin study after half a century: reflections on the past, and course for the future

Over the last 50 years Dunedin Study researchers have published more than 1400 peer-reviewed journal articles, books, and reports on many aspects of human health and development. In this 50th anniversary piece we reflect on (i) our historical roots and necessary re-invention through time; (ii) the underpinning principles that have contributed to our success; (iii) some selected examples of high-impact work from the behavioural, oral health, and respiratory domains; (iv) some of the challenges we have encountered over time and how to overcome these; and (vi) review where we see the Study going in the future. We aim to present some of the 'back story', which is typically undocumented and oft lost to memory, and thus focus on 'know-how'. Our hope is to humanise our research, share insights, and to acknowledge the real heroes of the Study - the 1037 Study members, their families and their friends, who have collectively given so much, for so long, in the hope of helping others.

Inhaled Marijuana and the Lung

Although vaping has recently increased as a mode of inhaling marijuana and has been associated with numerous and sometimes fatal cases of acute severe lung injury, smoking remains the most common method of inhaling marijuana and has been studied more extensively. Smoking marijuana has been shown to produce modest but significant short-term bronchodilation both in healthy subjects and those with asthma. Long-term effects of habitual marijuana smoking include the following: 1) symptoms of chronic bronchitis (increased cough, sputum production and wheezing); 2) modest effects on lung function in cross-sectional studies (no significant decrease in forced expired volume in 1 second [FEV₁) but mild reductions in FEV₁/forced vital capacity ratio [FEV₁/FVC], an increase in FVC and other lung volumes, reductions in specific airway conductance, and variable effects of maximal mid-expiratory flow rates and diffusing capacity; and 3) variable effects on age-related decline in FEV1 in longitudinal studies. Most cohort and case-control studies have failed to show that marijuana smoking is a significant risk-factor for lung cancer despite the presence of pro-carcinogenic components in marijuana smoke, although further study is warranted. The question whether marijuana smoking is associated with asthma is unclear and requires further investigation. Although delta-9 tetrahydrocannabinol (THC), the principal psychoactive component of marijuana, has immunomodulatory properties that hypothetically could increase the risk of pneumonia, the few available studies in marijuana smokers have failed to find an increased risk of pneumonia in immunocompetent users, although effects in immunosuppressed individuals have been variable.

Lifetime cannabis exposure and small airway function in a population-based cohort study

Background and objective

The long-term effects of cannabis on small airway function remain unclear. We investigated associations between cannabis use and small airway function in a general population sample.

Methods

Cannabis use was ascertained at multiple ages from age 18 to 45 years and quantified as joint-years among 895 participants in the Dunedin Multidisciplinary Health and Development Study. Small airway function at ages 38 and 45 years was measured using impulse oscillometry (IOS) before and after inhalation of salbutamol. Analyses used multiple linear regression adjusting for tobacco use, body mass index and height. Longitudinal analyses of cannabis use between 38 and 45 years also adjusted for IOS at age 38 years.

Results

Associations between lifetime cannabis joint-years and IOS differed between men and women: in women, cannabis use was associated with pre-bronchodilator resistance at 5 Hz (R 5) and 20 Hz (R 20), reactance at 5 Hz, area of reactance and resonant frequency, and marginally associated with the difference between R 5 and R 20. Cannabis use was only statistically significantly associated with pre-bronchodilator resonant frequency in men. Cannabis use between the ages of 38 and 45 years was associated with a similar pattern of changes in IOS measures. After salbutamol, cannabis use was only statistically significantly associated with R 5 and R 20 among women and none of the IOS measures among men.

Conclusions

Cannabis use is associated with small airway dysfunction at age 45 years, indicating an increase in peripheral airway resistance and reactance. These associations were greater and mostly only statistically significant among women. Associations were weaker and mostly nonsignificant after bronchodilator use, suggesting that cannabis-induced changes in small airways may be at least partially reversible.