Primary care

Relation between hormone replacement therapy and ischaemic heart disease in women: prospective observational study

E Løkkegaard, research fellow, ^a A T Pedersen, senior registrar, ^a B L Heitmann, professor, ^e Z Jovanovic, statistician, ^c N Keiding, professor, ^c Y A Hundrup, master of nursing, ^d E B Obel, consultant, ^d B Ottesen, professor. ^b

^a Department of Obstetrics and Gynaecology, Hvidovre University Hospital, Kettegård alle 30, DK-2650 Hvidovre, Denmark, ^b Juliane Marie Centre, H:s Rigshospitalet, University of Copenhagen, DK-2100 Copenhagen, Denmark, ^c Department of Biostatistics, Panûm Instituttet, University of Copenhagen, ^d Danish Nurse Study, National Institute of Public Health, DK-2100 Copenhagen, Denmark, ^e Research Unit for Dietary Studies, Institute of Preventive Medicine, Copenhagen University Hospital, DK-1399 Copenhagen, Denmark

Correspondence to: E Løkkegaard loekkegaard{at}dadlnet.dk

Objective: To investigate the risk of ischaemic heart disease and myocardial infarction among women using hormone replacement therapy, especially the potential modifying effect of cardiovascular risk factors.
Design: Prospective observational study.
Setting: Denmark.
Participants: 19 898 nurses aged 45 and over completing a questionnaire on lifestyle and use of hormone replacement therapy in 1993.
Main outcome measures: All cases of death and incident cases of ischaemic heart disease and myocardial infarction until the end of 1998.
Results: Current users of hormone replacement therapy smoked more, consumed more alcohol, had lower self rated health, but were slimmer and had a lower prevalence of diabetes than never users. In current users compared with never users, hormone replacement therapy had no protective effect on ischaemic heart disease (hazard ratio 1.2, 0.9 to 1.7) or myocardial infarction (1.0, 0.6 to 1.7), whereas current users with diabetes had an increased risk of death (3.2, 1.4 to 7.5), ischaemic heart disease (4.2, 1.4 to 12.5), and myocardial infarction (9.2, 2.0 to 41.4) compared with never users with diabetes.
Conclusion: Hormone replacement therapy showed no protective effect on ischaemic heart disease, but there was a significantly increased risk of death from all causes and ischaemic heart disease among women with diabetes.

What is already known on this topic Observational studies have shown that hormone replacement therapy protects women against ischaemic heart disease Randomised clinical trials found no such effect Little attention has focused on identifying subgroups of women who would or would not benefit from treatment What this study adds Hormone replacement therapy does not protect against ischaemic heart disease Women with diabetes who use hormone replacement therapy are at an increased risk of death from all causes and ischaemic heart disease