{
  "abstract": "Background Asthma exhibits a marked sex-based disparity suggesting sex hormones may influence asthma outcomes. To investigate this, we explored the relationship between exogenous sex hormones and asthma exacerbations using population-level data. Previously, we found the progesterone-only oral contraceptive pill was associated with an increased risk of exacerbations, only in women <35 years old. Here we focus on hormone replacement therapy (HRT). Only one study has previously investigated HRT; they found only previous HRT use – not current - was associated with exacerbations. There was no clear biological explanation for this unexpected finding.Methods We used UK electronic health records to draw a cohort of women with asthma aged 45–60, comparing HRT initiators to non-users. Women were censored at two years or end of follow-up; HRT users were also censored upon stopping HRT. We used inverse-probability of treatment weighting and Cox proportional hazards to estimate associations with exacerbations. Covariates included age, BMI, asthma severity (exacerbation history, inhaler use), comorbidities (e.g., atopy, depression), smoking, and socioeconomic status. Interaction analyses assessed effect modification by HRT type, BMI, and type 2 inflammation (blood eosinophils).Results A total of 182,010 women were included, of whom 9,663 (5.1%) used HRT and 172,347 did not. Among HRT users, 51.5% were prescribed combined HRT, 46.3% oestrogen-only, and 2.2% progesterone-only. In the overall cohort, 15% only used reliever inhalers, 47% used inhaled corticosteroids, and 35% used combination inhalers. Additionally, 23% experienced an exacerbation in the year prior to inclusion.HRT use was not associated with asthma exacerbations (weighted-HR=0.97, 95%CI 0.90–1.09, p=0.441). The association was not modified by HRT type, BMI or type 2 inflammation (all interaction p-values>0.05).Conclusion We found no association between HRT and asthma exacerbations, regardless of HRT type, BMI or type-2 inflammation. These findings differ from the previous HRT study, which may have been affected by temporality bias. However, our findings appear to align with those from our oral contraceptive study. Taken together, we hypothesis that the addition of exogenous sex hormone – specifically progesterone – may only be associated with asthma exacerbations in younger women with higher endogenous progesterone levels. This warrants further investigation.",
  "authors": [
    {
      "affiliations": [
        "National Heart and Lung Institute, London, UK"
      ],
      "name": "H Anpalagan"
    },
    {
      "affiliations": [
        "National Heart and Lung Institute, London, UK"
      ],
      "name": "B Lee"
    },
    {
      "affiliations": [
        "National Heart and Lung Institute, London, UK"
      ],
      "name": "T Tan"
    },
    {
      "affiliations": [
        "National Heart and Lung Institute, London, UK"
      ],
      "name": "E Wong"
    },
    {
      "affiliations": [
        "National Heart and Lung Institute, London, UK"
      ],
      "name": "C Bloom"
    }
  ],
  "title": "S130 Association between HRT use and asthma attacks: a UK population-based cohort",
  "uid": "d22b116f-7ded-57b4-a9b3-8fc28bd56ca6"
}