Women with the common conditions of endometriosis or growths in their uterus have a slightly higher risk of dying before the age of 70, a large US-based study said on Thursday.

One in 10 women worldwide suffers from endometriosis, a chronic disease in which tissue similar to the lining of the uterus grows outside the womb.

Up to a quarter of women are thought to have non-cancerous growths in their uterus called uterine fibroids.

Despite so many having these conditions, both are considered under-researched -- with some blaming a historically male-focused medical establishment for overlooking health problems that affect women.

Previous research has linked both conditions to a higher risk of some potentially deadly diseases, such as heart disease and some types of cancer.

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The new study in the BMJ journal analysed data from more than 110,000 women in the United States whose health has been monitored every two years since 1989.

This kind of observational research cannot directly prove cause and effect.

From the data, the researchers found that patients with one or both conditions had a slightly higher risk of dying before 70.

This was because the patients were more likely to get the other health problems suggested by previous research, the study indicated.

For uterine fibroids, the increase in early death was linked to a higher risk of gynaecological cancers, the study said.

These cancers were also the main cause of death among patients with endometriosis, though there were other factors including heart and respiratory diseases.

People with endometriosis had between a nine and 30 per cent higher risk of dying before 70 compared to people who did not have these linked health problems, the study said.

"These findings highlight the importance" of doctors looking out for these health problems in patients with endometriosis and uterine fibroids, the authors of the study said.

While historically overlooked, health conditions that only affect women are receiving more attention from researchers and policymakers.

This has particularly been the case for endometriosis, which can cause serious pain during periods and infertility -- and for which there is no known cure.