- The risk of developing new-onset asthma was lower among reproductive-age women who used hormonal contraceptives compared with those who did not.
- Risk reduction was similar with combined contraceptives and progestogen-only therapy.
- The beneficial role of hormonal contraceptives was greater for longer duration of use vs shorter duration.
Why this matters
- Findings may provide the basis for undertaking a clinical trial to investigate the safety and effectiveness of hormonal contraceptives for primary prevention of asthma.
- This population-based cohort study included 564,896 women (age, 16-45 years) who were followed for up to 17 years using data from the Optimum Patient Care Research Database, UK (2000-2016).
- Funding: Asthma and Health Data Research UK.
- At baseline, 26% of women were using any contraceptives (20% combined contraceptives and 6% progestogen-only contraceptives).
- During the 17 years (median of 6 years) of follow-up, 25,288 women developed asthma (incidence rate, 7.0 [95% CI, 6.9-7.1] per 1000 person-years).
- Compared with non-use, the risk of new-onset asthma was lower with previous use of:
- any contraceptives (adjusted HR [aHR], 0.70; 95% CI, 0.68-0.72);
- combined contraceptives (aHR, 0.70; 95% CI, 0.68-0.72); and
- progestogen-only contraceptives (HR, 0.70; 95% CI, 0.67-0.74).
- For current use:
- any contraceptives (aHR, 0.63; 95% CI, 0.61-0.65);
- combined contraceptives (aHR, 0.65; 95% CI, 0.62-0.67); and
- progestogen-only contraceptives (aHR, 0.59; 95% CI, 0.56-0.62).
- Longer duration of use was associated with a lower risk of asthma onset:
- 1-2 years (aHR, 0.83; 95% CI, 0.81-0.86);
- 3-4 years (aHR, 0.64; 95% CI, 0.61-0.67); and
- >5 years (HR, 0.46; 95% CI, 0.44-0.49).
- Retrospective design.
- Study could not define the routes of administration and dosages of hormonal contraceptives.