Objective: We investigated whether use of HRT and duration of use was associated with risk of developing asthma in peri- and post-menopausal women.
Methods: We constructed a 17-year (1/1/2000 – 12/31/2016) open cohort of 353,173 women (46-70 years old) from the Optimum Patient Care Database, a longitudinal primary care database from across UK. HRT use, subtypes, and duration of use; confounding variables; and asthma onset were defined using the Read Clinical Classification System. We fitted multilevel Cox regression models to estimate hazard ratios (HR) with 95% confidence intervals (CIs).
Results: During 17-year follow-up (1,340,423 person-years), 7,614 new asthma cases occurred, giving an incidence rate of 5.7 (95%CI 5.5-5.8) per 1,000 person-years. Compared to non-use of HRT, previous use of any (HR 0.83; 95%CI 0.76-0.88), estrogen-only (HR 0.89; 95%CI 0.84-0.95), and combined estrogen/progestogen (HR 0.82; 95%CI 0.76-0.88) HRT were associated with a reduced risk of asthma onset. This was also the case with current use of any (HR 0.79; 95%CI 0.74-0.85), estrogen-only (HR 0.80; 95%CI 0.73-0.87), and combined estrogen/progestogen (HR 0.78; 95%CI 0.70-0.87) HRT. Longer duration of HRT use (1-2 years: HR 0.93; 95%CI 0.87-0.99; 3-4 years: HR 0.77; 95%CI 0.70-0.84; 5+ years: HR 0.71; 95%CI 0.64-0.78) was associated with a dose-response reduced risk of asthma onset.
Conclusion: We found that HRT was associated with a reduced risk of developing late onset asthma in menopausal women. Further cohort studies are needed to confirm these findings.