The HERS trial1 did in fact show harm. The event rate in the first year was 50% higher in patients undergoing HRT (19 excess events). Although the control group almost caught up later (with 17 excess events), these events occurred later, resulting in an overall loss of roughly 2.3 patient-years per 100 patients treated. Additionally, there were 22 more thromboembolic events and 11 more deaths (all due to coronary heart disease [CHD])in the HRT group. Statistics are not particularly helpful in evaluating unexpected findings, but the play of chance on the anticipated positive effect would not plausibly produce the HERS result.
Blakely JA. Increased Coronary Events, HERS, and HRT: Any Connection?—Reply. Arch Intern Med. 2001;161(10):1350-1351. doi: