title: Associations between cancer and Parkinson's disease in U.S. elderly adults.
abstract: Several studies suggest that cancer is reduced before and after a Parkinson's disease (PD) diagnosis. However, determining relationships among diseases of ageing is challenging due to possible biases in ascertaining disease. This study evaluates the PD and cancer relationship, addressing potential biases.
  
  
  
  Using Surveillance, Epidemiology, and End Results-Medicare linked data (1992-2005) of adults ≥ 65 years, we assessed PD risk after cancer comparing PD in 743 779 cancer patients with PD in a non-cancer group (n = 419 432) in prospective cohort analyses. We also conducted a case-control study of 836 947 cancer cases and 142 869 controls to assess cancer following PD. We applied Cox proportional hazards models to estimate hazards ratios (HRs) for PD after cancer and unconditional logistic regression to estimate odds ratios (ORs) for PD preceding cancer, controlling for physician visits and other factors. To explore biases in ascertaining cancer, we examined relationships between cancer and automobile accident injuries, which we expected to be null.
  
  
  
  No association was observed between cancer and subsequent PD [HR = 0.97; 95% confidence interval (CI) = 0.92-1.01] nor between cancer and subsequent automobile injuries (HR = 1.03; 95% CI = 0.98-1.07). One site, lung cancer, was associated with subsequent reduced PD, which may reflect confounding by smoking. In the case-control analysis, PD was associated with reduced subsequent cancer, overall (OR = 0.77; 95% CI = 0.71-0.82) and for several cancer sites. However, the automobile injury/ subsequent cancer association was similar (OR = 0.83; 95% CI = 0.78-0.88), suggesting a cancer detection bias after serious health outcomes.
  
  
  
  In totality, our data do not support a biological relationship between PD and cancer.
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA freedmam@mail.nih.gov.
authors.forename: D Michal
authors.initials: DM
authors.lastname: Freedman
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, MD, USA.
authors.forename: Jincao
authors.initials: J
authors.lastname: Wu
authors.affiliation: National Institute of Environmental Health Sciences, Aging and Neuroepidemiology Group, Research Triangle Park, NC, USA.
authors.forename: Honglei
authors.initials: H
authors.lastname: Chen
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Engels
authors.affiliation: National Cancer Institute, Division of Cancer Control and Population Sciences, Rockville, MD, USA and.
authors.forename: Lindsey R
authors.initials: LR
authors.lastname: Enewold
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA.
authors.forename: Neal D
authors.initials: ND
authors.lastname: Freedman
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Goedert
authors.affiliation: University of Redlands, Department of Biology, Redlands, CA, USA.
authors.forename: Ralph W
authors.initials: RW
authors.lastname: Kuncl
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA.
authors.forename: Mitchell H
authors.initials: MH
authors.lastname: Gail
authors.affiliation: National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, MD, USA.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Pfeiffer
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D006278:Medicare; D009369:Neoplasms / Q000453:epidemiology*; D010300:Parkinson Disease / Q000453:epidemiology*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D018426:SEER Program; D017678:Sex Distribution; D012907:Smoking / Q000453:epidemiology; D014481:United States / Q000453:epidemiology
keywords: : Cancer; Medicare; Parkinson’s disease; SEER Program