- In women, worsening of asthma is seen due to fluctuations in the levels of hormones like estrogen and progestogen during menstrual cycle.
- Combination pills containing estrogen and progestogen are more effective in reducing risk of severe bouts of asthma than progestogen-only pills.
- Irrespective of BMI and smoking, reduced risk was seen in patients taking combination pill for 3-4 years and 5 plus year.
In women who are of reproductive age hormonal contraceptive pills is associated with a reduced risk of having severe bouts of asthma.
The study was published in the journal Thorax
The female sex hormones include estrogen and progestogen. Hormonal contraceptives contain these hormones either in combination or progestogen only pills.
Differences in the severity and incidence of asthma are seen clearly between males and females. In women worsening of the asthma symptoms is seen due to fluctuations in the level of these hormones due to menstrual cycle.
No consensus has been yet reached although the impact of synthetic sex hormones on asthma has repeatedly studied over several decades. In order to clear these uncertainties, a study was conducted to observe the impact of different contraceptives and their period of use on severity of asthma. They also studied the impact of weight gain (BMI) and smoking.
Optimum Patient Care Research Database (OPCRD) contains the health records of more than 6 million patients across UK. They used this database to find women of reproductive age (16-45) who also had asthma.
From the start of 2000 the end of 2016, hospital admissions emergency care department visits, and prescriptions for asthma treatment were tracked and a total of 83, 084 women were found.
Current and previous hormonal contraceptive use - combined estrogen/progestogen and progestogen-only, for different durations of 1-2years, 3-4 years or 5+ years was compared with no use of hormonal contraceptives.
Potentially influential factors included number of pregnancies, smoking, BMI, deprivation, and wide range of gynecological conditions like endometriosis, PCOS, absence of periods, fibroids and hysterectomy.
At the start of the study - 34% of the women were using hormonal contraceptives: 25% combined; 9% progestogen-only.
With increase in age, BMI and number of pregnancies proportion of women who had bouts of severe asthma increased. This number was also higher in current and previous smokers and among women who had gynecological conditions.
After taking into consideration the potentially influential factors, it was observed that current and previous use of combined hormonal contraceptives was associated with a relatively small risk of severe asthma bouts when compared to no use at all.
However the decrease in risk was observed only in patients who are taking oral contraceptives for 3-4 years or more than 5 years. These results were seen irrespective of BMI and smoking status.
However in patients taking progestogen-only contraceptive pill, no protective effect was seen irrespective of BMI and smoking.
The cause couldn't be established as this was an observational study. The researchers also stated that it is not possible to exclude the impact of other unidentified factors. How the synthetic sex hormones affect asthma is not clear hence further research will be needed to explore the underlying biological processes.
Lead author Dr Bright Nwaru said," There's an intriguing relationship between sex and asthma. And over the past 40 years many studies have been published trying to understand why boys have a higher incidence of asthma than girls. But starting from around the time of puberty this changes, and asthma becomes more common in women than men."
He also added,"I don't think this finding will end up in clinical guidelines or advice. But...the signal we've got from the study gives us the confidence to progress to designing more studies to try to understand the mechanisms through which hormonal contraceptives may influence asthma."