Risk of Stroke or Acute Myocardial Infarction in Subconjunctival Hemorrhage: A Nationwide Cohort Study.

PURPOSE To investigate whether subconjunctival hemorrhage (SCH) raises the risk of subsequent stroke or acute myocardial infarction (AMI) in the general population. METHODS Using the National Health Insurance Service-National Sample Cohort database records from 2002 to 2013. Of 1,025,340 individuals in the database, we included 703,090 aged ≥ 20 years old without any history of SCH, cerebrovascular diseases, and ischemic heart diseases in the analyses. Of these, we identified 46,251 cases of incident SCH and regarded it as a time-varying covariate. We performed sensitivity analyses using 1:4 propensity score (PS)-based matched controls. To adjust for potential confounders, we investigated Cox regression models using defined demographic information, comorbidities, co-medications, and the Charlson Comorbidity Index score. RESULTS The SCH group showed higher incidence probability of stroke or AMI than the general population (3.17% versus 2.71%, respectively; p < .001); however, when compared to the PS-based matched controls, there was no difference (3.17% versus 3.03%, respectively; p = .76). Time-varying covariate Cox regression analyses without adjusting for confounders showed that SCH was associated with increased risk of subsequent stroke or AMI; however, after adjusting for confounders, SCH did not increase the risk of stroke or AMI. CONCLUSION This population-based cohort study showed that SCH itself is not a risk factor for stroke or AMI. Clinicians could reassure patients with SCH that it would not increase the risk for stroke or AMI. We recommend attentive evaluation of underlying diseases for patients with SCH for identifying risk factors of stroke or AMI.