Opium Use and Risk of Pancreatic Cancer: A Prospective Cohort Study

Background: We examined the association between opium consumption and pancreatic cancer incidence in a large-scale prospective cohort of the general population in Northeast of Iran. Methods: A total of 50,045 adults were systematically followed-up (median of 7.4 years) and incident cases of pancreatic cancer were identified. Self-reported data on opium consumption was collected at baseline. Cumulative use (-year) was defined as number of nokhods (a local unit, approximately 0.2 g) of opium consumed per day multiplied by number of years consuming. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between opium consumption and pancreatic cancer were calculated using Cox proportional hazards regression models. Results: Overall, 54 confirmed cases of pancreatic cancer were identified. Opium use of more than 81 nokhod-years (high cumulative use), compared to never use, was strongly associated with pancreatic cancer even after adjustments for multiple potential confounding factors [HR=3.01; 95% CI 1.25-7.26]. High cumulative consumption of opium was significantly associated with risk of pancreatic cancer after adjusting for cumulative dose of cigarette smoking [HR=3.56; 95% CI 1.49-8.50]. In a sensitivity analysis, we excluded participants (including 2 pancreatic cancer cases) who were recruited within the first 5 years of starting opium consumption; high cumulative use of opium was still associated with pancreatic cancer risk [HR=2.75; 95% CI 1.14-6.64]. Conclusion: Our results showed a positive association between opium consumption and pancreatic cancer. Impact: This is the first prospective large-scale study to show the association of opium consumption with pancreatic cancer as a risk factor.