Hormonal contraceptives tied to lower risk of new-onset asthma in reproductive-age women

Takeaway

• 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.

• Findings may provide the basis for undertaking a clinical trial to investigate the safety and effectiveness of hormonal contraceptives for primary prevention of asthma.

Study design

• 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.