title: Diabetes and the risk of developing Parkinson's disease in Denmark.
abstract: OBJECTIVE
  Insulin contributes to normal brain function. Previous studies have suggested associations between midlife diabetes and neurodegenerative diseases, including Parkinson's disease. Using Danish population registers, we investigated whether a history of diabetes or the use of antidiabetes drugs was associated with Parkinson's disease.
  
  
  METHODS
  From the nationwide Danish Hospital Register hospital records, we identified 1,931 patients with a first-time diagnosis of Parkinson's disease between 2001 and 2006. We randomly selected 9,651 population control subjects from the Central Population Registry and density matched them by birth year and sex. Pharmacy records comprising all antidiabetes and anti-Parkinson drug prescriptions in Denmark were available. Odds ratios (ORs) were estimated by logistic regression models.
  
  
  RESULTS
  Having diabetes, as defined by one or more hospitalizations and/or outpatient visits for the condition, was associated with a 36% increased risk of developing Parkinson's disease (OR 1.36 [95% CI 1.08-1.71]). Similarly, diabetes defined by the use of any antidiabetes medications was associated with a 35% increased Parkinson's disease risk (1.35 [1.10-1.65]). When diabetes was defined as the use of oral antidiabetes medications, effect estimates were stronger in women (2.92 [1.34-6.36]), whereas when diabetes was defined as any antidiabetes drug prescription, patients with early-onset Parkinson's disease were at highest risk (i.e., Parkinson's disease diagnosed before the age of 60 years; 3.07 [1.65-5.70]).
  
  
  CONCLUSIONS
  We found that a diagnosis of, or treatment received for, diabetes was significantly associated with an increased risk of developing Parkinson's disease, especially younger-onset Parkinson's disease. Our results suggest a common pathophysiologic pathway between the two diseases. Future studies should take age at Parkinson's disease onset into account.
authors.affiliation: Channing Laboratory, Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA. eva.schernhammer@channing.harvard.edu
authors.forename: Eva
authors.initials: E
authors.lastname: Schernhammer
authors.forename: Johnni
authors.initials: J
authors.lastname: Hansen
authors.forename: Kathrine
authors.initials: K
authors.lastname: Rugbjerg
authors.forename: Lene
authors.initials: L
authors.lastname: Wermuth
authors.forename: Beate
authors.initials: B
authors.lastname: Ritz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003718:Denmark / Q000453:epidemiology; D003920:Diabetes Mellitus / Q000453:epidemiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010300:Parkinson Disease / Q000453:epidemiology* / Q000209:etiology*; D012307:Risk Factors