Association Between Bipolar Disorder or Schizophrenia and Oral Anticoagulation Use in Danish Adults With Incident or Prevalent Atrial Fibrillation

IMPORTANCE: Individuals with bipolar disorder or schizophrenia have a higher risk of adverse outcomes from cardiovascular diseases. Oral anticoagulation therapy (OAT) for patients with atrial fibrillation (AF) is needed for stroke prevention, but whether patients with bipolar disorder or schizophrenia face disparities in receiving this therapy is unknown. OBJECTIVE: To assess whether bipolar disorder or schizophrenia is associated with a lower rate of OAT initiation in patients with incident AF and lower prevalence of OAT in those with prevalent AF. DESIGN, SETTING, AND PARTICIPANTS: A nationwide cohort study of Danish patients with AF was conducted from January 1, 2005, to December 31, 2016, and data were analyzed from January 1 to June 15, 2020. Data from national registries included information on all redeemed prescriptions and all hospital contacts of all patients with incident or prevalent AF (age, 18-100 years) and increased risk status, defined by a CHA(2)DS(2)-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, stroke or transient ischemic attack, vascular disease, age 65-74 years, sex category) risk score greater than or equal to 2. EXPOSURES: Hospital diagnosis of bipolar disorder or schizophrenia. MAIN OUTCOMES AND MEASURES: Adjusted proportion differences for OAT initiation and OAT prevalence, comparing individuals with and without bipolar disorder or schizophrenia. RESULTS: Patients included with incident AF (n = 147 810) had a mean (SD) age of 76.9 (10.1) years, 78 577 (53.2%) were women, 1208 (0.8%) had bipolar disorder, and 572 (0.4%) had schizophrenia. Accounting for age, sex, and calendar time, bipolar disorder and schizophrenia were associated with significantly lower frequency of OAT initiation within 90 days after incident AF (bipolar disorder: −12.7%; 95% CI, −15.3% to −10.0%; schizophrenia: −24.5%; 95% CI, −28.3% to −20.7%) and lower OAT prevalence in patients with prevalent AF (bipolar disorder: −11.6%; 95% CI, −13.9% to −9.3% schizophrenia: −21.6%; 95% CI, −24.8% to −18.4%). Adjusting for socioeconomic factors and other comorbid conditions attenuated these associations, particularly for patients with bipolar disorder. However, schizophrenia continued to be associated with a with a lower rate of OAT initiation (−15.5%, 95% CI, −19.3% to −11.7%) and a −12.8% (95% CI, −15.9% to −9.7%) lower OAT prevalence. These associations were also present after the introduction of non–vitamin K antagonists (adjusted proportion difference in 2013-2016: −12.4%; 95% CI, −18.7% to −6.1% for initiation and −10.1%; 95% CI, −13.8% to −6.4% for prevalence). CONCLUSIONS AND RELEVANCE: In this study, patients with bipolar disorder or schizophrenia were less likely to receive OAT in the setting of AF. For patients with bipolar disorder, this deficit was largely associated with socioeconomic factors and comorbidities, especially toward the end of the study period. For patients with schizophrenia, disparities in this stroke prevention therapy persistently exceeded what could be explained by other patient characteristics.