Asthma development associated with hormonal contraceptive use during adolescence
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Key takeaways:
- Initiation of hormonal contraception was associated with a 1.78 hazard ratio for developing new asthma.
- Cumulative risk for new asthma was 2.7% after 3 years among patients using hormonal contraception.
Girls who began hormonal contraceptive treatment before age 18 years experienced greater risk for developing asthma than girls who did not, according to a study published in the Journal of Allergy and Clinical Immunology: In Practice.
The cumulative risk for initiating treatment for asthma significantly increased within 3 years of beginning hormonal contraception, Erik Soeren Halvard Hansen, MD, PhD, department of respiratory medicine, Copenhagen University Hospital-Hvidovre, and colleagues wrote.
The exposure-density matched cohort study involved 184,046 girls and women aged 10 to 40 years, including 30,669 (mean age, 15.6 years) who had been treated with hormonal contraceptives and 153,377 (mean age, 15.5 years) who had not. On average, patients were followed for 763 days.
Patients who began hormonal contraception were more likely to be from families with higher incomes and live in densely populated areas than patients who did not receive such treatment. This treatment had a mean length of 1,050 days.
The most common types of hormonal contraception to patients receiving it for the first time included second-generation (83%) and third-generation oral pills (12%), both of which combined estrogen and progestin.
The researchers defined new asthma as two redeemed prescriptions for inhaled corticosteroids within 2 years or as registration of an ICD-10 code of J45, both without any previously filled prescriptions.
Patients who began hormonal contraception of any kind were 1.78 times more likely to later initiate treatment for asthma (95% CI, 1.58-2), after adjusting for urbanization and household income. Without adjustments, the hazard ratio was 1.76 (95% CI, 1.56-1.98), which the researchers called similar.
After 3 years, cumulative risks for initiating asthma treatment included 2.7% among patients treated with hormonal contraceptives and 1.5% among those who did not receive such treatment.
When the researchers defined asthma as one filled prescription instead of two, risks for developing asthma after 3 years increased to 4% for those patients who were receiving hormonal contraceptives and 2.4% for those who were not.
Patients using second-generation hormonal contraception methods combining estrogen and progestin had a hazard ratio of 1.73 (95% CI, 1.47-2.04) for initiating daily treatment for asthma, whereas those on third-generation combination methods had a hazard ratio of 1.5 (95% CI, 1.04-2.17).
Fourth-generation methods were not associated with any significant risk for developing asthma, the researchers said, but patients using progestin-only oral pills had a 2.95 hazard ratio (95% CI, 1.59-5.49).
Hormonal contraceptive treatment began at a mean of age 15.6 years, and 88.9% of the patients began treatment between age 14 years and age 17 years. Hazard ratios for developing initiating treatment for asthma by age included:
- age 10 to 13 years: 2.16 (95% CI, 1.47-3.2);
- age 14 to 17 years: 1.71 (95% CI, 1.5-1.95); and
- age 18 years and older: 1.34 (95% CI, 0.37-4.8).
Cumulative risks for developing asthma among patients using hormonal contraceptives compared with those patients who did not use hormonal contraceptives based on age included:
- age 10 to 13 years: 3.6% (95% CI, 2.4-4.7) for users vs. 1.6% (95% CI, 1.4-1.9) for nonusers;
- age 14 to 17 years: 2.7% (95% CI, 2.3-3) for users vs. 1.5% (95% CI, 1.4-1.6) for nonusers; and
- age 18 years and older: 1.1% (95% CI, 0-2.4) for users vs. 0.9% (95% CI, 0-1.4) for nonusers.
Considering these associations with increases in asthma incidence among girls aged 10 to 17 years, the researchers advised physicians to evaluate any airway symptoms that manifest after initiation of hormonal contraception treatment for asthma. The researchers also called for studies investigating whether these contraceptives trigger airway reactions.
Perspective
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I do find these findings surprising! We don’t generally worry about asthma risk when prescribing any form of birth control to our patients, and we counsel patients who already have asthma that there are no restrictions in the type of birth control they can safely use. This aligns with the CDC, which constantly looks at all the evidence on how different medical conditions affect different types of contraception and publishes formal recommendations. The CDC also doesn’t consider asthma a reason to avoid any certain type of birth control.
As the authors of this paper say themselves, some research already has found the opposite of this study — that asthma improves with using hormonal birth control. So, it is an unexpected set of findings.
But if these findings are true, are they significant? That is, do they make a difference in patient health or in how we counsel patients choosing between different birth control options? While the authors did look at a huge number of patients — more than 18,000 — the increase in asthma risk that they found was really small: a difference in only one percentage point of increased risk overall. And this risk was only among patients aged younger than 18 years. Patients aged 18 years and older did not have any increased risk for asthma with hormonal contraceptive use. Very young patients, aged 10 to 13 years when they started using hormonal contraception, had the highest increased risk, but even their overall difference was only a 2% increased risk.
So, it is hard to know whether these findings are a true association, given the conflicting results that already exist in the literature. And even if we think it is a true association, it is hard to know how to weigh a possible very small increased risk for developing asthma among young adolescents starting hormonal contraception.
I can confidently say I have not seen patients with new asthma diagnoses or worsening asthma after starting contraception. I don't often see patients aged younger than 14 years starting hormonal contraception, and age 10 to 13 years was the age group that the authors found most likely to have an increased risk, so it might be related to the patients I’m seeing. But generally, we do not see a clinical connection between hormonal contraception and lung disease.
Until more data arise to clarify the connection, if any, between hormonal contraception and asthma risk, I would not necessarily change our OBGYN practices. Modern hormonal contraception allows patients to safely avoid unintended pregnancy, and this is a real and important benefit. We know that pregnancy itself brings with it many other health risks, including worsening asthma in about a third of patients!
Of course, if an individual patient tells me that her hormonal contraception feels like it is worsening her asthma, or honestly causing any other symptom that is bothersome to her, we can always work together to find something she prefers. There are many forms of effective contraception, some without any hormones at all, and patients should never feel like they have to stick to only one option!
Big population studies like this study are great, because they can do research with so much patient data. But they are also hard because they might not have access to the real clinical outcome they care about. This study, for example, could only look at whether patients got a prescription for a steroid inhaler, not whether they had wheezing, or worsening shortness of breath, or admissions to the hospital for asthma, or any of the other symptoms that affect how people experience asthma. Future research that looks directly at these clinical outcomes will be important.
Additionally, this study used the Danish National Patient Register to collect patient data. It might be that trends found among a patient population only in Denmark may not be found among a more genetically heterogenous group of people, or even among people from different climates. I look forward to seeing future research on this question among patients with more varied ethnic and racial backgrounds.
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