Washington - A new study has suggested that some women may have more or fewer asthma symptoms depending on where they are in their menstrual cycle.
Researchers said spikes and dips in oestrogen and other hormones likely affect the lungs and other physiological responses involved in breathing.
However, itâ€™s still unclear whether the findings could improve doctorsâ€™ treatment of women with asthma, News 24 reported.
Dr Ferenc Macsali of Haukeland University Hospital in Bergen, Norway, and colleagues surveyed close to 4 000 women in Northern Europe who had normal periods and werenâ€™t taking birth control pills.
Along with other health and lifestyle questions, they asked women to report when their last period started, as well as whether theyâ€™d had any breathing-related problems in the past three days.
Just under 8 percent had been diagnosed with asthma. Between 2 percent and 6 percent reported recent wheezing, coughing and/or shortness of breath.
They found that the number of women with each of those symptoms changed depending on where they were in their menstrual cycle. For example, wheezing spiked just before and just after mid-cycle (ovulation).
The dip in between corresponds to peaks in oestrogen, follicle stimulating hormone and luteinizing hormone, the researchers wrote in the American Journal of Respiratory and Critical Care Medicine, in a paper released.
Complaints of shortness of breath and coughing both declined just after women got their periods, and shortness of breath was also more rare right before menses started.
Dr Macsaliâ€™s team saw cyclical patterns in breathing symptoms in women with and without asthma.
What explains those patterns is still up for debate. Oestrogen may affect the lungs directly, the researchers said.
Insulin resistance and markers of general inflammation are known to vary during the menstrual cycle, which could also play a role in when breathing symptoms get better or worse, they noted.
â€śThe observed patterns in our study are most likely a result of complex hormonal processes and it does not seem plausible that one sex hormone should explain the variation in respiratory symptoms during the menstrual cycle,â€ť the researchers wrote.
Women with asthma should â€śbe aware of a possibility that their symptoms are influenced by day in cycle,â€ť Dr Macsali said.