Decreased Risk of Intracerebral Hemorrhage Among Patients With Milder Allergic Rhinitis.

Background: This study investigated whether allergic rhinitis (AR) increases the risk of intracerebral hemorrhage (ICH). Methods: Using Taiwanese insurance outpatient claims data, 52 870 patients with new diagnoses of AR between 2000 and 2010 were identified, and 105 680 age- and sex-frequency matched people without AR were chosen randomly as controls. Risks of ICH were correlated with AR and comorbidities, such as diabetes, hypertension, coronary artery disease, hyperlipidemia, disease and chronic kidney disease, and were estimated by the end of 2011. Results: The risk of ICH was lower in the AR cohort than in the comparison cohort, with an adjusted hazard ratio (aHR) of 0.58 (95% confidence interval [CI] = 0.50-0.66), assessed using the multivariable Cox model. Age-specific analysis demonstrated that the aHR for ICH in the AR patients increased with age, with an aHR of 0.53 (95% CI = 0.39-0.71) in the a parts per thousand currency sign49-year age group, which increased to 0.72 (95% CI = 0.59-0.89) in the elderly age group. The risk of ICH increased with the severity of AR, from an aHR of 0.47 (95% CI = 0.40-0.56) in mild AR patients to 2.55 (95% CI = 1.88-3.47) in severe ones. For patients without comorbidities, the risk of ICH was 0.46 times (95% CI = 0.34-0.63) lower in the AR cohort than in the comparison cohort. Conclusion: This study showed for the first time that milder AR is correlated with a reduction in the risk of ICH, particularly for elderly patients.