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HRT and hip fractures


Replacement of endogenous with exogenous oestrogen reduces the risk of hip fracture, as a large case-control study from Sweden shows [1].

Study


All hip fractures between late 1993 and early 1995 in women born in 1914 or after in six Swedish counties covering about 4.3 million people were found from hospital discharge records. After excluding those for which there was an obvious cause (trauma, dementia, cancer etc) there were 1644 cases. Controls (over 3000) were women born in Sweden randomly selected from a population register.

Cases were sent a comprehensive questionnaire about three months after the fracture. Controls were sent the same questionnaire. This asked about reproductive history and use of exogenous oestrogens, including oral contraceptives and hormone replacement therapy, as well as demographic, dietary and other questions.

Results


Eighty-two percent of women answered the questionnaires. The main results are shown in the Table. Compared with never users, there was a substantial decrease in fracture risk with ever users of replacement therapy, though this came predominately from the reduced risk for current users. For current users there was a 9% decrease in risk of hip fracture for every year of use. Five years after the last use of hormone replacement therapy no substantial protective effect against hip fracture remained, though a protective effect was seen in the five years after use of hormones when they had been used for at least five years (Table).

Main results on hip fracture risk and HRT use
  Odds ratio* (95% CI) Percent risk decrease for each year of therapy (95% CI)
Ever user 0.58 (0.46 to 0.75) 6 (3 to 9)
Current users of HRT 0.35 (0.24 to 0.53) 9 (5 to 13)
Former users 0.76 (0.57 to 1.01) 3 (7 to -2)
Last use 1-5 years, duration >5 years 0.27 (0.08 to 0.94) not applicable
* compared with never users of hormone replacement therapy


In sub-group analyses a common finding was that these general results were much the same irrespective of the type of hormone replacement therapy. Oral or transdermal therapy, with or without progestins, all had much the same protective effect for current users, and protective effects were evident with progestins structurally related to progesterone and to testosterone.

Comment


The key message is that hormone replacement therapy protects against hip fracture while it is being taken and for a few years afterwards. Continued protection needs continued use.

Reference:

  1. K Michaëlsson et al. Hormone replacement therapy and risk of hip fracture: population based case-control study. British Medical Journal 1998 316: 1858-1863.



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