Women who begin hormone replacement therapy during perimenopause and continue for at least ten years before their final period may significantly reduce their risk of serious health conditions, new research suggests. The study indicates these women could face around 60% lower odds of developing breast cancer, heart attacks, or strokes compared to women who start treatment later or never use hormones.
Researchers from Case Western Reserve University analysed more than 120 million patient records to examine the timing of oestrogen therapy. They compared women who started treatment during perimenopause - the transitional phase before menopause that can last up to a decade - with those who began after menopause or never received hormone treatment.
Treatment timing proves crucial
The findings reveal stark differences based on when women begin hormone therapy. Women who started oestrogen treatment after menopause showed only modest benefits, with slightly lower risks of breast cancer and heart attacks compared to those who never took hormones.
However, post-menopausal hormone users faced a 4.9% higher likelihood of stroke, the study found. This contrasts sharply with the substantial protective effects seen in women who began treatment during perimenopause.
Menopause typically occurs between ages 45 and 55 when hormone levels drop and periods cease permanently. The preceding perimenopause phase brings symptoms including irregular periods, hot flushes, mood changes, and sleep difficulties.
Research challenges current practice
Lead author Ify Chidi said the study aimed to explore whether hormone therapy could deliver benefits beyond symptom relief. "There has long been a debate about if and when oestrogen therapy should begin, so hopefully the use of large-scale electronic health record data will help resolve that question," she stated.
The researcher added: "The goal of this study was to explore whether oestrogen therapy could do more than relieve symptoms, and the results suggest that early initiation could be a key factor in reducing morbidity." The findings were presented at the annual meeting of the Menopause Society in Orlando.
Current NHS guidance notes that HRT can slightly increase breast cancer risk, with approximately five additional cases per 1,000 women taking HRT for five years. The National Institute for Health and Care Excellence advises against prescribing HRT to patients with current, past, or suspected breast cancer.
Expert reaction mixed on findings
Dr Stephanie Faubion from the Menopause Society acknowledged the research's potential significance whilst noting limitations. "The findings of this study suggest lower risk and potentially greater benefit of oestrogen-based therapy when started in perimenopause," she said.
She cautioned that the observational study design carries "known potential biases such as healthy user bias" but suggested the results "may pave the way for additional research on the risks and benefits of hormone therapy when initiated earlier in the menopause transition."
Dr Kotryna Temcinaite from Breast Cancer Now emphasised that hormone therapy decisions remain highly personal. "Whether and when to start taking HRT to help with menopause symptoms is a very personal choice," she said, noting that around two in every 100 breast cancers in the UK are thought linked to HRT use.
Risk factors vary by treatment type
Dr Temcinaite explained that breast cancer risk differs significantly depending on the type of hormone therapy used. "We already know that the risk of breast cancer is higher with combined HRT (containing oestrogen and progestogen) than with oestrogen-only HRT," she said.
She added that risk increases "the longer you take HRT or if you started taking it at an older age." The expert noted that whilst the findings are promising, further research is needed to understand whether oestrogen-only HRT itself is solely responsible for these protective effects.
Sources used: "Case Western Reserve University", "The Menopause Society", "Breast Cancer Now", "NHS", "NICE"
Note: This article has been edited with the help of Artificial Intelligence.
