A Cochrane review included 19 studies with a total of 40 410 post-menopausal women. The studies compared hormone therapy for 6 months or more (oestrogen, with or without progestogen) with placebo or no treatment. Most participants were post-menopausal American women, and the mean age in most studies was over 60 years. The length of time women were on treatment varied across the studies from 7 months to 10.1 years.
Hormone therapy in both primary and secondary prevention conferred no protective effects for death (RR 1.01, 95% CI 0.92 to 1.11; 14 studies, n=35 483), death from cardiovascular causes (RR 0.96, 95% CI 0.78 to 1.18; 9 studies, n=33 613), non-fatal myocardial infarction (RR 1.01, 95% CI 0.89 to 1.14; 14 studies, n=34 841), angina (RR 0.90, 95% CI 0.79 to 1.03; 5 studies, n=30 502), or revascularisation procedures (RR 0.95, 95% CI 0.85 to 1.05; 6 studies, n=30 724) compared to placebo. However, there was an increased risk of stroke in those in the hormone therapy arm for combined primary and secondary prevention (RR 1.24, 95% CI 1.10 to 1.41; 10 studies, n=34 672). Venous thromboembolic events were increased (RR 1.92, 95% CI 1.36 to 2.69; 10 studies, n=37 313), as were pulmonary emboli (RR 1.81, 95% CI 1.32 to 2.48; 7 studies, n=36 316) on hormone therapy relative to placebo. The associated numbers needed-to-harm (NNH) were 165, 118 and 242 for stroke, venous thromboembolism and pulmonary embolism respectively. Results for primary and secondary prevention separately are shown in tables and .
Those who started hormone therapy less than 10 years after the menopause had lower mortality (RR 0.70, 95% CI 0.52 to 0.95; 5 studies, n=9 088) and coronary heart disease risk (composite of death from cardiovascular causes and non-fatal myocardial infarction) (RR 0.52, 95% CI 0.29 to 0.96; 4 studies, n=8 311), though they were still at increased risk of venous thromboembolism (RR 1.74, 95% CI 1.11 to 2.73; 3 studies, n=9 838) compared to placebo or no treatment. In those who started treatment more than 10 years after the menopause it had little effect on death or coronary heart disease between groups but there was an increased risk of stroke (RR 1.21, 95% CI 1.06 to 1.38; 8 studies, n=22 722) and venous thromboembolism (RR 1.96, 95% CI 1.37 to 2.80; 9 studies, n=27 475).
| Outcome | Participants (studies) | Assumed risk (placebo) | Corresponding risk (HT) | Relative effect (95% CI) |
|---|---|---|---|---|
| Death (all causes) | 34 422 (8 studies) | 32 per 1000 | 32 per 1000 (29 to 36) | RR 1 (0.89 to 1.12) |
| Death (CV causes) | 28 353 (3 studies) | 8 per 1000 | 7 per 1000 (4 to 11) | RR 0.81 (0.47 to 1.40) |
| Stroke | 28 719 (4 studies) | 18 per 1000 | 23 per 1000 (20 to 28) | RR 1.32 (1.12 to 1.56) |
| Venous thromboembolism | 33 477 (6 studies) | 10 per 1000 | 20 per 1000 (13 to 31) | RR 1.92 (1.24 to 2.99) |
| Pulmonary embolism | 31 732 (3 studies) | 5 per 1000 | 9 per 1000 (5 to 15) | RR 1.89 (1.17 to 3.04) |
| Outcome | Participants (studies) | Assumed risk (placebo) | Corresponding risk (HT) | Relative effect (95% CI) |
|---|---|---|---|---|
| Death (all causes) | 5 445 (7 studies) | 84 per 1000 | 88 per 1000 (73 to 105) | RR 1.04 (0.87 to 1.24) |
| Death (CV causes) | 5 259 (6 studies) | 45 per 1000 | 45 per 1000 (35 to 58) | RR 1.00 (0.78 to 1.29) |
| Stroke | 5 172 (5 studies) | 65 per 1000 | 71 per 1000 (58 to 86) | RR 1.09 (0.89 to 1.33) |
| Venous thromboembolism | 4 399 (6 studies) | 11 per 1000 | 23 per 1000 (13 to 40) | RR 2.02 (1.13 to 3.62) |
| Pulmonary embolism | 3 920 (3 studies) | 4 per 1000 | 10 per 1000 (4 to 27) | RR 2.48 (0.92 to 6.70) |
The following decision support rules contain links to this evidence summary: