Prospective case–control study of nonfatal cancer preceding the diagnosis of parkinson’s disease

Abstract

Prior studies suggest a decreased frequency of cancer in patients with Parkinson's disease (PD). We conducted a nested case-control study to estimate the association between the diagnosis of PD and a history of preceding cancer. Our case-control study was nested within a prospective cohort of 22,071 US male physicians. During 22 years of follow-up, 487 incident cases of PD were identified and matched by age to 487 controls. We then evaluated a history of cancer prior to the index date that was confirmed by medical record review. The frequency of any cancer was less in cases (13.1%) than in controls (14.8%). There was an inverse relationship between overall cancer (odds ratio [OR] = 0.83; 95% CI, 0.57-1.21), smoking-related (OR = 0.74; 95% CI, 0.35-1.57), and non-smoking-related cancer (OR = 0.88; 95% CI, 0.59-1.32) and the subsequent development of PD. Smoking significantly modified the relationship between PD and smoking-related cancer (p (interaction) = 0.002). PD cases who smoked had an OR of 0.32 (95% CI, 0.11-0.89) for smoking-related cancer. In contrast, PD cases who never smoked had an OR of 6.85 (95% CI, 0.83-56.39). Our data suggest that the frequency of cancer preceding the diagnosis of PD is decreased. Smoking status prior to PD or cancer diagnosis significantly modified the association between smoking-related cancer and PD.