A new study suggests that woman’s menstrual cycle affects the severity of respiratory symptoms, potentially worsening conditions such as asthma.

Norwegian researchers studied almost 4,000 women, and found worse symptoms around ovulation.

Writing in the American Journal of Respiratory and Critical Care Medicine, they said it may be possible to adapt women’s medication.

All the women studied had regular menstrual cycles lasting 28 days or less, and none were taking hormonal contraceptives.

Of those studied, 28.5% were smokers and 8% had been diagnosed with asthma.

Wheezing symptoms were worse between days 10 to 22 of cycles, with a slight dip near the point of ovulation for most.

Shortness of breath was worse on days seven to 21, again with a slight fall around ovulation.

The study found it was not just women diagnosed with asthma who experienced these symptoms and variations.

Coughing was worse following ovulation for those with asthma, those who were overweight and smokers.

When an individual woman has her period is determined by complex hormonal processes over the course of her cycle.

Throughout, levels of different hormones rise and fall – and body temperature rises around ovulation.

The researchers suggest that these fluctuations may have direct effects on airways. and indirect effects on inflammatory responses to infection.

Writing in the journal, the researchers led by Dr. Ferenc Macsali, of the Haukeland University Hospital in Bergen, Norway, said: “We found that respiratory symptoms varied significantly during the menstrual cycle.

“There were large changes in symptom incidence through the cycle for all symptoms.”

They also found “pronounced” symptom variations during the menstrual cycle in women with asthma, and say the findings suggest women might need tailored medication regimes.

“Adjustment of asthma medication to the menstrual cycle may potentially improve the efficacy of asthma treatment and reduce disability and health costs related to asthma in women.”

Dr. Ferenc Macsali added: “Our results point to the potential for individualizing therapy for respiratory diseases according to individual symptom patterns.

“Adjusting asthma medication, for example, according to a woman’s menstrual cycle might improve its efficacy and help reduce disability and the costs of care.”