A new United Kingdom study has suggested that fluctuations in female sex hormones could play a role in the development of asthma and allergies in women, possibly explaining the differences between men and women in the incidence and severity of the condition.

Carried out by researchers from the University of Edinburgh, the major review analyzed more than 50 studies which together looked at more than 500,000 women with asthma from puberty to 75 years of age.

The results showed a link between asthma symptoms and key changes in a woman’s life such as puberty and menopause, with women who started their periods before turning 11 years old and those entering menopause found to have a higher risk of developing asthma compared to those who started menstruation later or who were pre-menopause.

Irregular periods were also found to be associated with a higher rate of the condition.

Many women also reported that their asthma symptoms change with their menstrual cycle, which the team suggested may be due to fluctuations in levels of hormones such as estrogen and progesterone.

The onset of menopause also causes estrogen and progesterone levels to vary; however, the team noted that the link between asthma and these hormones still remains unclear.

They also added that as the relationship between asthma and hormonal drugs such as HRT and contraceptives is unclear women should continue to take medications as prescribed by their GP.

“In carrying out this systematic review, we noted that there were many differences between studies investigating hormonal treatments in terms of the type and dose of hormone, and the way patients took the treatment. This made it difficult to draw firm conclusions from the results. We are now undertaking a project to clarify the role of contraceptives and HRT in asthma and allergy symptoms,” commented lead researcher Nicola McCleary.

Although the team stressed that more research is needed, they noted that further studies could help explain why asthma is more common in boys than girls in childhood, but more common and more severe in teenage girls and women following puberty.

Asthma affects more than five million people in the U.K. It is a respiratory condition which can cause serious difficulties breathing and is often associated with allergies.

The results were published in the Journal of Allergy and Clinical Immunology. JB

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