title: Formulations of hormone therapy and risk of Parkinson's disease.
abstract: Hormone therapy (HT) is a class of medications widely prescribed to women in the Western world. Evidence from animal models and in vitro studies suggests that estrogen may protect against nigrostriatal system injury and increase dopamine synthesis, metabolism, and transport. Existing epidemiologic research indicates a possible reduced risk of Parkinson's disease (PD) associated with HT use. The objective of this study was to evaluate PD risk associated with specific HT formulations. Neurologist-confirmed cases and age-matched controls were identified from Group Health Cooperative (GHC) of Washington State. Final analysis included 137 female cases and 227 controls. Hormone therapy use was ascertained from the GHC pharmacy database, further classified as conjugated estrogens, esterified estrogens, and progestin. Ever use of HT formulation demonstrated a suggested elevated risk with esterified estrogen use (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.0-9.8), and no risk associated with conjugated estrogen use (OR, 0.6; 95% CI, 0.6-1.3). Restricting this analysis to prescriptions that included progestin further elevated the risk associated with esterified estrogen use (OR, 6.9; 95% CI, 2.1-22.9); again, no risk was associated with conjugated estrogen use (OR, 1.7; 95% CI, 0.6-5.0). The findings from this study suggest an increase in PD risk associated with esterified estrogen use combined with progestin, and no risk associated with conjugated estrogen with progestin. These findings could have important implications for choice of HT in clinical practice.
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA.
authors.forename: Jessica I
authors.initials: JI
authors.lastname: Lundin
authors.forename: Thanh G N
authors.initials: TG
authors.lastname: Ton
authors.forename: Andrea Z
authors.initials: AZ
authors.lastname: LaCroix
authors.forename: W T
authors.initials: WT
authors.lastname: Longstreth
authors.forename: Gary M
authors.initials: GM
authors.lastname: Franklin
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Swanson
authors.forename: Terri
authors.initials: T
authors.lastname: Smith-Weller
authors.forename: Brad A
authors.initials: BA
authors.lastname: Racette
authors.forename: Harvey
authors.initials: H
authors.lastname: Checkoway
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D015914:Estrogen Replacement Therapy / Q000009:adverse effects; D042724:Estrogens, Esterified (USP) / Q000009:adverse effects* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008875:Middle Aged; D010300:Parkinson Disease / Q000209:etiology*; D011372:Progestins / Q000009:adverse effects*
chemical_list: D042724:Estrogens, Esterified (USP); D011372:Progestins
keywords: Parkinson's disease; epidemiology; estrogen therapy; hormone therapy; neurodegenerative disease