Progestin-only birth control pill increases risk of asthma attacks

Progestin-only oral contraceptives may expose asthmatic women to more asthma attacks than combined oral contraceptives. This effect is particularly noticeable in young women under 35.A recent study involved just over 130,000 women between 18 and 50 years who had been diagnosed with asthma. In this cohort, new users of oral contraceptives were compared with women who had not been users for at least 12 months, to observe the effect of exogenous hormones on asthma attacks.Women were excluded from the study if they had chronic obstructive pulmonary disease (COPD), had not received asthma medication in the last year, were pregnant or were using non-oral contraceptives (intrauterine device, injections, skin patch, vaginal ring, etc.).“From adolescence onwards, asthma is more prevalent and severe in women than in men. Sex hormones, particularly progesterone, certainly play a role, but we don't fully understand the mechanisms,” said the U.K.-based researchers who carried out the study.By isolating only the effect of the contraceptive pill on asthma attacks, no effect was observed, regardless of the hormone used in the contraceptive's composition.Progesterone comboHowever, the results became more worrying when certain variables were grouped together, notably the age of the participants and the type of oral contraceptive. In women under 35, the use of a progestin-based oral contraceptive exposed them to a 39% greater risk of asthma attacks (HR 1.39, 95% CI 1.12-1.72) compared with those who used no hormonal contraception. This effect disappeared in women over 35.“In younger women, the combination of endogenous and exogenous progesterone would cause an excess of this sex hormone, whereas towards the end of the 30s, progesterone levels drop drastically,” the study authors said to explain this finding. In non-human models, it has been reported that high progesterone levels may exacerbate airway inflammation and bronchial hyperactivity.High eosinophil counts in women on progestin-only oral contraceptives were also reported to increase the risk of asthma attacks by 24% (HR = 1.24, 95% CI 0.97-1.58). As for women with low corticosteroid use combined with progesterone-based oral contraception, this would amplify the risk of asthma attacks by around 20% (HR 1.20, 95% IC 1.03-1.40). In vitro data show that exogenous progesterone attenuates the anti-inflammatory effect of corticosteroids by interfering with the glucocorticoid receptor.Importantly, not all these effects apply to oral contraceptives combining both estrogen and progestin, reinforcing progesterone's role in asthma pathophysiology.The researchers therefore advocate a personalized approach to enable women and healthcare professionals to make an informed decision on the best oral contraceptive to use according to their situation.The results are published in the journal ERJ Open Research.

Progestin-only birth control pill increases risk of asthma attacks

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