Risk of developing avascular necrosis of the femoral head and neck among patients with bipolar disorder: A nationwide cohort study

Background and objectives: The association between bipolar disorder (BD) and avascular necrosis of the femoral head and neck (AVNHNF) remains unclear. We aimed to investigate the risk of AVNHNF among different polarity of BD. Methods: Between 2001 and 2010, patients with BD were selected from the Taiwan National Health Research Database. The controls were individuals without severe mental disorder who were matched for demographic, medical and psychiatric comorbidities. Cox regression analysis was used to estimate the risk of AVNHNF, with adjustments for demographics, comorbidities, exposure to corticosteroids, and all-cause clinical visits. Results: A total of 84,721 patients with BD and 169,442 controls were included. Patients with BD demonstrated a 1.92-fold (95% of confidence interval: 1.21–3.04) higher risk of AVNHNF compared with the controls. The risk was increased to 7.91-fold (4.32–14.49) in patients with severe BD compared with the controls. Importantly, patients with severe bipolar depression were associated with a 14.23-fold higher risk of AVNHNF compared with the controls, while those with sever bipolar mania were associated with a 3.55-fold higher risk. Compared with the controls with alcohol use disorder (AUD), patients with BD and comorbid AUD were associated with a 2.0-fold higher risk of AVNHNF. Finally, long-term use of atypical antipsychotics was associated with a decreased risk of AVNHNF). Conclusion: Clinicians should be aware of the increased risk of AVNHNF among patients with BD. This increased risk was associated with disorder severity, polarity, and comorbidity with AUD, and attenuated by long-term atypical antipsychotic treatment.