Original Research Article

Oral contraceptives and the risk of asthma attacks: a population-based cohort study

ERJ Open Research 2025 01278-2024; DOI: https://doi.org/10.1183/23120541.01278-2024
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Abstract

Background

The role that sex hormones play in asthma remains unclear. The oral contraceptive pill (OCP), commonly used by younger women, acutely increases sex hormones providing an opportunity to observe their effect.

Objective

Evaluate the association between OCP and asthma attacks.

Methods

Using the UK's Clinical Practice Research Datalink, linked to hospital admission and mortality data, 2004 to 2020, we observed women with asthma (18–50 years), comparing OCP never-users to new-users; separated into a combined oral contraceptive (COC) cohort and progestogen-only (POP) cohort. We applied inverse-probability of treatment weighting and Cox proportional hazards, accounting for demographics, asthma severity/control and comorbidities. Additionally, we stratified by potential modifiers: age, BMI, blood eosinophils (x109 cells·L−1, normal <0.3, eosinophilia ≥0.3) and corticosteroid use (lower use: ≤3 inhaled corticosteroids prescriptions, higher use: ≥4 inhaled and/or oral corticosteroids).

Results

132 676 and 129 151 were eligible for the COC and POP cohorts, respectively. There was no association between COC, or POP, and asthma attacks (weighted-HR, 95% CI: COC=1.00, 0.89–1.13; POP=1.11, 0.97–1.28). However, POP association was modified by asthma phenotype and corticosteroid use, but not BMI, after accounting for asthma severity/control, demographics and comorbidities. In the POP users, women who were younger than 35 years old (1.39, 1.12–1.72), those with eosinophilia (1.24, 0.97–1.58), or those with lower corticosteroid use (1.20, 1.03–1.40) had an elevated risk of asthma attacks.

Conclusions

Commencing exogenous progesterone without an estrogen component (POP) was associated with increased asthma attacks in asthma phenotypes including in younger women, eosinophilic-asthma, and women with lower corticosteroid use.

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Footnotes

This manuscript has recently been accepted for publication in the ERJ Open Research. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJOR online. Please open or download the PDF to view this article.

Conflict of interest: Bohee Lee reports support for the present study from Asthma+Lung UK.

Conflict of interest: Chloe Bloom reports support for the present study from Asthma+Lung UK; grants from National Institute for Health and Social Care Research.

Conflict of interest: Ernie Hoi Cheung Wong reports consultancy fees from AstraZeneca Plc; payment or honoraria for lectures, presentations, manuscript writing or educational events from AstraZeneca Plc, Chiesi Limited; support for attending meetings from GSK Plc.

Conflict of interest: The remaining authors have nothing to disclose.

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