title: Hormone therapy and Alzheimer disease dementia: new findings from the Cache County Study.
abstract: OBJECTIVE
  Observational studies suggest reduced risk of Alzheimer disease (AD) in users of hormone therapy (HT), but trials show higher risk. We examined whether the association of HT with AD varies with timing or type of HT use.
  
  
  METHODS
  Between 1995 and 2006, the population-based Cache County Study followed 1,768 women who had provided a detailed history on age at menopause and use of HT. During this interval, 176 women developed incident AD. Cox proportional hazard models evaluated the association of HT use with AD, overall and in relation to timing, duration of use, and type (opposed vs unopposed) of HT.
  
  
  RESULTS
  Women who used any type of HT within 5 years of menopause had 30% less risk of AD (95% confidence interval 0.49-0.99), especially if use was for 10 or more years. By contrast, AD risk was not reduced among those who had initiated HT 5 or more years after menopause. Instead, rates were increased among those who began "opposed" estrogen-progestin compounds within the 3 years preceding the Cache County Study baseline (adjusted hazard ratio 1.93; 95% confidence interval 0.94-3.96). This last hazard ratio was similar to the ratio of 2.05 reported in randomized trial participants assigned to opposed HT.
  
  
  CONCLUSIONS
  Association of HT use and risk of AD may depend on timing of use. Although possibly beneficial if taken during a critical window near menopause, HT (especially opposed compounds) initiated in later life may be associated with increased risk. The relation of AD risk to timing and type of HT deserves further study.
authors.affiliation: Department of Public Health, Weill Cornell Medical College, New York, NY, USA.
authors.forename: Huibo
authors.initials: H
authors.lastname: Shao
authors.forename: John C S
authors.initials: JC
authors.lastname: Breitner
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Whitmer
authors.forename: Junmin
authors.initials: J
authors.lastname: Wang
authors.forename: Kathleen
authors.initials: K
authors.lastname: Hayden
authors.forename: Heidi
authors.initials: H
authors.lastname: Wengreen
authors.forename: Chris
authors.initials: C
authors.lastname: Corcoran
authors.forename: Joann
authors.initials: J
authors.lastname: Tschanz
authors.forename: Maria
authors.initials: M
authors.lastname: Norton
authors.forename: Ron
authors.initials: R
authors.lastname: Munger
authors.forename: Kathleen
authors.initials: K
authors.lastname: Welsh-Bohmer
authors.forename: Peter P
authors.initials: PP
authors.lastname: Zandi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000139:chemically induced / Q000453:epidemiology* / Q000517:prevention & control*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008593:Menopause / Q000187:drug effects*; D012307:Risk Factors; D013997:Time Factors