Why women take HRT
A woman's medical history has a greater influence over whether she takes hormone replacement therapy than lifestyle factors or social background, according to a report1 published today.
Based on the habits and history of more than a million UK women aged between 50 and 64, the report shows that around half used HRT at some stage and one third were currently taking the drug.
The research from the Million Women Study - a collaboration between Cancer Research UK, the Medical Research Council and the National Health Service Breast Screening Programme - showed that factors such as education or which part of the country a woman comes from were less influential than a history of breast cancer or cardiovascular disease.
The women were invited to attend the NHS Breast Screening Programme between 1996-2000 and answer questions about their use of HRT, past health, lifestyle, reproductive factors and socio-demographics.
Of the women studied, 66 per cent of those who had had both ovaries removed and 48 per cent of those who had had a hysterectomy took HRT compared with 27 per cent among women who had neither.
Among women with a history of breast cancer, six per cent were currently using HRT, compared to 24 per cent among women with a history of stroke or blood clots and 34 per cent among women who reported no previous cancer or cardiovascular disease.
In comparison, the variation by lifestyle or geographical region was small - for instance 30 per cent of Scottish women took HRT compared to 35 per cent in Southeast England.
Dr Emily Banks, of the Cancer Research UK Epidemiology Unit at the University of Oxford and author of the report, says: "This is the largest study of its kind in the world and the first to bring together detailed national information of women's use of HRT with other health factors.
"It shows that large numbers of women in their 50's and 60's have been exposed to HRT for prolonged periods of time and it sheds some light on how this group of women compare with the rest of the population."
Dr Gillian Reeves, co-author of the report, adds: "The differences between women who use HRT and those who don't - especially the fact that users are less likely to have had cancer or cardiovascular disease compared to non-users - make evaluation complex.
"Future studies have to be very careful when investigating the effects of HRT. The Million Women Study provides a solid basis for investigating HRT in the long term."
Julietta Patnick, National Coordinator of the Screening Programme, says: "This study will provide a baseline from which we can start to understand more about the impact HRT has on women's bodies as they age.
"All the women participating in the study are also participating in the NHS Breast Screening Programme, and we are very grateful for the important contribution made by these women."
Sir Paul Nurse, Chief Executive of Cancer Research UK, said: "One of the most important things about this study is that its findings are based on the biggest ever number of women who have answered questions about their health and lifestyle.
"This means we will be able to understanding more about risk factors in disease and improve our knowledge of women's health."
- British Journal of Obstetrics and Gynaecology109 pp.1319-1330