Joint Surgery Predicted By Number Of Children And Use Of HRT

According to a study published in the Annals of the
Rheumatic Diseases, women who have many
children, used hormone replacement therapy, and had early puberty are
more likely to have surgery performed on their joints - especially on
their knees.



Researchers from the United Kingdom studied 1.3 million middle-aged UK
women who took part in the Million Women Study. The health of the
participants was tracked beginning around age 50, and they were
monitored for about six years. Baseline information provided data on
the age of the participants when they had their first and last
menstrual events, how many children to whom they had given birth, and
their use of oral contraceptives and hormone replacement therapy (HRT).
The researchers used the follow-up data to see if the women were
admitted to hospital for a knee or hip replacement for the inflammatory
joint disease, osteoarthritis.



Dr Bette Liu (Cancer Epidemiology Unit, University of Oxford, Oxford,
UK) and colleagues report that over 12,000 of the women needed a hip
replacement and a little less than 10,000 required a knee replacement
during the follow-up time period.



What factors most predicted these surgeries? Serial motherhood - or
having additional children - increased the probability of a hip
replacement by 2% and of a knee replacement by 8%. Women who began
menstruation before the age of 11 increased their likelihoods of both
types of surgery by 9 to 15%. The researchers found that previous use
of oral contraceptives did not seem to have a significant effect on the
risk of joint surgery. However, use of HRT raised the probability of a
hip replacement by 38% and of a knee replacement by 58%.



The researchers point out that women on HRT are probably making better
use of health services, which may partly explain their highly
likelihood of joint surgery. They also suggest that female sex
hormones, such as estrogen, may help explain the difference in
osteoarthritis, a condition that is more common among women than men.



"Given the large burden of osteoarthritis and the associated burden of
joint replacement surgery in women worldwide, it is important to
understand the role of potentially modifiable factors for these
conditions. We found that parity, age at menarche and HRT use are all
associated with the risk of hip and knee replacement and that the knee
joint is affected more by these factors than the hip joint. However the
underlying reasons for these findings remain unclear," conclude the
authors.



Reproductive history, hormonal factors and the incidence of
hip and knee replacement for osteoarthritis in middle-aged women

B Liu, A Balkwill, C Cooper, A Roddam, A Brown, V Beral, on behalf of
the Million Women Study Collaborators

Annals of the Rheumatic Diseases (2008).

doi:10.1136/ard.2008.095653

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Here to View Journal Website



: Peter M Crosta