Oestrogen-containing postmenopausal hormone therapies are associated with a reduced risk of cardiovascular disease. Some studies suggest this effect may depend on when therapy is started, but this has not been tested.
US researchers carried out a randomised trial in which they assigned 643 postmenopausal women to either oestrogen-containing hormone therapy or placebo. Carotid-artery intima-media thickness (CIMT) was used to assess progression of atherosclerosis.
After an average of five years, women who received therapy within six years of menopause had a significantly lower annual increase in CIMT than those who received placebo. However, this was not observed in women who started therapy ten or more years after menopause.
The researchers say their findings, published in The
New England Journal of Medicine (online, 31 March 2016)
, provide the first direct evidence that timing of hormone therapy is critical for preventing atherosclerosis progression.
 Hodis HN, Mack WJ, Henderson VW et al. Vascular effects of early versus late postmenopausal treatment with estradiol. New England Journal of Medicine 2016;374:1221–1231. doi: 10.1056/NEJMoa1505241