Recency and duration of postmenopausal hormone therapy: effects on bone mineral density and fracture risk in the National Osteoporosis Risk Assessment (NORA) study.

OBJECTIVES: Results from the Women's Health Initiative showed that postmenopausal hormone replacement therapy (HRT) prevents fractures but has an overall unfavorable risk:benefit ratio, leading to the recommendation that HRT be used only for women with troublesome menopause symptoms, and for as short a time as possible. This recommendation has important implications for the timing and duration of HRT and the prevention of osteoporosis. The large number of women participating in the National Osteoporosis Risk Assessment (NORA) program provided the opportunity to evaluate bone mineral density (BMD) and 1-year fracture risk in analyses stratified by duration and recency of HRT.
DESIGN: Participants were 170,852 postmenopausal women aged 50 to 104, without known osteoporosis, who were recruited from primary physicians offices across the US. BMD was measured at one of four peripheral sites, and the 1-year risk of osteoporotic fracture was assessed by questionnaire.
RESULTS: At baseline, current HRT users had the highest T-scores at every age. Among current hormone users, women who had used HRT longest had the highest BMD levels. Women who had stopped HRT more than 5 years previously, regardless of duration of use, had T-scores similar to never-users. Current but not past hormone use at baseline was associated with a 25% to 29% lower risk of osteoporotic fracture (P < 0.0001) in 1 year, compared with nonusers. These findings were independent of age, ethnicity, body mass index, lifestyle, years postmenopausal, and site of BMD measurement.
CONCLUSIONS: We conclude that postmenopausal BMD and fracture are closely associated with current, but not prior, HRT use. Use of HRT for 5 years or less, as proposed for treatment of symptomatic women during menopause transition, is unlikely to preserve bone or significantly reduce fracture risk in later years.