Association between waterpipe smoking and lung cancer: a multicentre case-control study in Iran

OBJECTIVES

This study investigated the association between lung cancer and waterpipe smoking, which is an emerging global public health concern.

STUDY DESIGN

Multicentre case-control study.

METHODS

This study included 627 cases and 3477 controls from the Iranian Study of Opium and Cancer (IROPICAN) study, which was conducted between 2017 and 2020. One frequency-matched control for each lung cancer patient was selected by age, gender and residential place; however, this study used controls of four cancer types in the analyses. The multivariable logistic regression model estimated the odds ratio (OR) and 95% confidence intervals (CIs). Additional analyses were performed among 181 lung cancer cases and 2141 controls who were not cigarette smokers or opium or nass/pipe users.

RESULTS

The odds of lung cancer were higher among waterpipe smokers than never-smokers (OR = 1.3, 95% CI: 1.0-1.7). Results showed a higher OR of lung cancer for those who smoked the waterpipe daily (OR = 2.1, 95% CI: 1.4-3.0), smoked more than two heads per day (OR = 2.7, 95% CI: 1.8-4.0), had smoked for >20 years (OR = 1.9, 95% CI: 1.3-2.7), smoked more than 20 head-years (OR = 2.8, 95% CI: 1.9-4.1) and initiated smoking before the age of 30 years (OR = 1.7, 95% CI: 1.1-2.5). The association was only statistically significant for squamous cell carcinomas (OR = 1.8, 95% CI 1.2-2.7). Furthermore, this study observed a higher OR of lung cancer among exclusive waterpipe smokers (OR = 2.3, 95% CI: 1.6, 3.5).

CONCLUSIONS

Waterpipe smoking was associated with an increased risk of lung cancer. The association was stronger with higher frequency, duration and intensity of exposure to waterpipe smoking. The association increases in exclusive waterpipe smokers, which is likely due to controlling for residual confounding by cigarette smoking and opium consumption, and higher exposure levels in this subpopulation.

National Study of Opium and Cancer in Iran (IROPICAN): Study Protocol and Results of the Pilot Phase

Background: Several epidemiologic studies have reported that opium consumption is associated with higher risk of cancer and may indeed cause cancer. However, most of these studies were not primarily designed to study the effect of opium on cancer. Therefore, control selection and data collections methods were not optimized for this purpose. Aim: We designed a large multicenter case-control study to specifically investigate the association between opium use and risk of 4 cancer types (i.e., lung, bladder, head and neck and colorectal cancers). We will recruit 800 cases and 800 controls for each cancer in this project. Methods: So far we have collected 70% of the cases and controls. We report here the study protocol and results of the pilot phase. Results: During the pilot phase, we determined that hospital visitors are the most appropriate type of controls; 185 cases and 176 controls were enrolled. Controls are matched to cases for sex, age and place of residence. Collection of data using a comprehensive questionnaire, focused on measuring use of opium and its derivatives, was feasible. Underreporting of opium was estimated to be 30% among controls. Collection of other data, including data tobacco and alcohol use, and nutritional data using a food frequency questionnaire, was feasible. Biologic samples including blood and saliva sample were collected from cancer cases and controls. Results of the pilot phase and validation study were used to optimize the full study protocol and questionnaires. Conclusion: The pilot phase of the study showed that the study is feasible, the best method of control selection is from hospital visitors, and both questionnaire and biologic samples can be collected. In addition of the results from pilot phase, preliminary results from the main phase of this study will be presented.