Higher Risk of Hyperthyroidism in People with Asthma: Evidence from a Nationwide, Population-Based Cohort Study

Studies have indicated that hyperthyroidism exacerbates asthma; however, the influence of asthma in the development of hyperthyroidism has not been adequately studied.The aim of this population-based, retrospective cohort study was to investigate the association between asthma and the development of hyperthyroidism.In this retrospective cohort study, datasets from the Longitudinal Health Insurance Database 2000 in Taiwan during 1997 to 2013 were retrieved. Patients newly diagnosed with asthma (International Classification of Diseases, Ninth Revision: 493) during 2000 to 2013 were identified as the exposure cohort. The 1:1 propensity-score-matched nonasthma individuals were selected as the comparison cohort. The hazard ratio (HR) of development of hyperthyroidism in patients with asthma and its association with age and follow-up time were examined.A total of 45,182 individuals were included in the study, including 22,591 and 22,591 patients with (asthma group) and without (control group) asthma, respectively. Incidence rates (per 100,000 person-months) of hyperthyroidism in the study groups were 12.88 in the control group and 16.95 in the asthma group. The adjusted HR for developing hyperthyroidism was 1.31 (95% confidence interval, 1.12-1.53) in patients with asthma compared with controls. The risk of developing hyperthyroidism was higher in patients with asthma aged>30 years old and with a follow-up of <3 years than in other subgroups.Patients with asthma had a higher risk of developing hyperthyroidism, especially those over 30 years of age and in the first 3 years after diagnosis of asthma. Clinicians caring for patients with asthma should be aware of this increased risk.