Use of oral contraceptives may lower the risk of hip fracture later in reproductive life, according to a report in the May 1st issue of the Lancet. Previous studies have shown a protective effect of postmenopausal oestrogen therapy on the risk of having a fracture. However, whether or not oral contraceptives, which also contain the hormone oestrogen, can confer a similar risk is not clear.
Dr Karl Michaëlsson and colleagues, from Sweden and the USA, collected data on all cases of hip fracture that occurred between October 1993, and February 1995, among women in Sweden. Questionnaires were then posted to these women who had had a hip fracture (the cases), and to a group of women who had not had a hip fracture (the control group) to ascertain details about the women's previous use of oral contraceptives.
Of the 1327 cases, 130 (11.6%) had used oral contraceptives. Of the 3312 controls, 562 (19.1%) reported previous use of oral contraceptives. The use of oral contraceptives was associated with a 25% reduction in risk of having a hip fracture later in life. Women who had previously taken an oral contraceptive containing a high dose of oestrogen had a 44% reduced risk of hip fracture.
Oestrogen in the oral contraceptive pill acts on bone, via a mechanism that is as yet unclear, making bones denser and stronger. After a woman has gone through menopause, her bone mass decreases naturally. The researchers postulatee that by increasing the bone mass before menopause, the mass will decrease by less overall, and state that oral contraceptive users appear to reach the menopause with a bone density 2 to 3% higher than that of non-users.
*Provided by The Lancet.
Contact: Dr Karl Michaëlsson, University Hospital, S 75185 Uppsala, Sweden
tel +46 18 663000; fax +46 18 509427; e-mail: Karl.Michaelsson@ortopedi.uu.se