Dr Shelley Salpeter and colleagues at Santa Clara Medical Centre, California, examined 19 studies involving 16,283 women with a mean age of 55 years.
They found HRT was associated with a 27 per cent reduction in relative mortality risk and an absolute risk reduction of around 1 per cent.
The research, published in the American Journal of Medicine, sought to 'make sense of the accumulated evidence' on HRT. The researchers specifically wanted to address concerns raised by a 2002 study of data from the Women's Health Initiative (WHI).
The WHI study showed women aged over 63 years had an increased risk of developing a variety of conditions. This led to the assumption that HRT might increase health risks in all women and that these risks raised women's mortality risk.
Dr Salpeter believes the WHI results have been poorly inter-preted. She hoped the new study would help clarify the role of HRT in younger women.
The researchers stressed their findings needed to be interpreted in light of potential benefits and harms of hormone therapy.
'Available evidence indicates that hormone therapy in younger postmenopausal women increases the risk of breast cancer and pulmonary embolism, and reduces risk of cardiovascular events, colon cancer, and hip fracture,' they said.
'The total mortality benefit for younger women seen in the randomised trials and observa-tional studies indicates that the reduction in deaths from coronary heart disease, fracture, and colon cancer outweighed the increase in deaths from breast cancer, stroke, and pulmonary embolism,' the researchers added.