Cannabis Use and Incidence of Testicular Cancer: A 42-Year Follow-up of Swedish Men between 1970 and 2011

Abstract

Background: Given current drug policy reforms to decriminalize or legalize cannabis in numerous countries worldwide, the current study assesses the relation between cannabis use and the development of testicular cancer.Methods: The study included a population-based sample (n = 49,343) of young men ages 18-21 years who underwent conscription assessment for Swedish military service in 1969-1970. The conscription process included a nonanonymous questionnaire eliciting information about drug use. Conscription information was linked to Swedish health and administrative registry data. Testicular cancers diagnosed between 1970 and 2011 were identified by International Classification of Diseases-7/8/9/10 testicular cancer codes in the Swedish National Patient Register, the Cancer Register, or the Cause of Death Register. Cox regression modeling was used to estimate the hazards associated with cannabis use and time to diagnosis of testicular cancer.Results: No evidence was found of a significant relation between lifetime "ever" cannabis use and the subsequent development of testicular cancer [n = 45,250; 119 testicular cancer cases; adjusted HR (aHR), 1.42; 95% confidence interval (CI), 0.83-2.45]. "Heavy" cannabis use (defined as usage of more than 50 times in lifetime, as measured at conscription) was associated with the incidence of testicular cancer (n = 45,250; 119 testicular cancer cases; aHR 2.57; 95% CI, 1.02-6.50).Conclusions: The current study provides additional evidence to the limited prior literature suggesting cannabis use may contribute to the development of testicular cancer.Impact: Emerging changes to cannabis drug policy should consider the potential role of cannabis use in the development of testicular cancer. Cancer Epidemiol Biomarkers Prev; 26(11); 1644-52. ©2017 AACR.

Figure 1

Cohort profile and flow-chart for final analytic sample and 42-year follow-up ^aExposure variables: “ever” use of cannabis before conscription and lifetime frequency of cannabis use; ^b Covariates: conscript’s birth year, history of cryptorchidism, parental testicular cancer, frequency of tobacco smoking and volume of alcohol drinking

Figure 2

Number of incident cases (n = 135) of testicular cancer diagnosed during follow-up time (1970–2011) among original sample of conscripts born in 1949–1951 (n = 49 343) by age at diagnosis across levels of cannabis use. * Information on drug use is unclear, missing or use of other drugs, but not cannabis indicated ** Defined as use of cannabis (with or without use of any other illicit drugs) ever before conscription more than 50+ times.