Introduction There is increasing evidence that cannabis smoking, combined with tobacco, increases the risk of emphysema and bullous lung disease (BLF Report 2012). The aim of this retrospective case study was to determine the prevalence of tobacco and/or cannabis smoking amongst patients < 50 years with radiologically-diagnosed emphysema, pneumothorax or bullous lung disease, and to assess the quality of smoking documentation.
Methods A list of all high-resolution computerised tomography (HRCT) scans over 2 years (Jan2010-Dec2012), of patients ≤50 years at scan date was generated from the radiology database. All scans were reviewed by a Consultant Thoracic Radiologist to confirm accuracy of initial reports. Case notes of all patients with radiological emphysema, pneumothorax or bullous lung disease were reviewed for tobacco and cannabis smoking histories to examine the relationship with abnormalities.
Results 361 HRCTs were performed over 2 years in ≤50 year olds. 91/361 (25.2%) scans were reported as emphysema, pneumothorax or bullae. 85/91 notes were available for analysis and 62/85 (73%) had full smoking histories recorded; 7/85(8.2%) tobacco smoking history not recorded and 22/85(25.9%) cannabis smoking history not recorded. 27/48 (56%) current tobacco smokers with an abnormal HRCT also smoke cannabis. There were no cannabis-only smokers and only 6/62 (9.7%) were never-smokers (tobacco&cannabis).
56/62 (90%) abnormal HRCTs were in ex/current tobacco smokers and 27/62 (44%) were in current tobacco&cannabis smokers. There was a higher prevalence of pneumothoraces and bullae with a cannabis and tobacco smoking history than for tobacco alone but this was not statistically significant different (chi-squared STATA) (Table1).
Conclusion More than half of tobacco smokers with abnormal HRCTs also had a history of previous and current cannabis smoking. Despite these findings 25% of patients with abnormal HRCTs had no documentation regarding cannabis smoking. This population of ≤50 years olds with abnormal HRCTs did not smoke cannabis without tobacco. While not statistically significant, bullae and pneumothoraces were more frequently observed in patients who smoked tobacco with cannabis compared to tobacco alone. Larger studies are needed to further understand the additive effect of cannabis smoking to tobacco-induced lung damage. These studies will require systematic recording of both tobacco and cannabis smoking histories.