Excess incidence and risk factors for recurrent pneumonia in bipolar disorder

Aim: Patients with bipolar disorder (BD) tend to have poorer outcomes after pneumonia and could have a higher risk for recurrence of pneumonia. We aimed to investigate the incidence and risk factors of recurrent pneumonia in patients with BD.

Methods: In a nationwide cohort of BD patients (derived from the National Health Insurance Research Database in Taiwan) who were hospitalized for pneumonia between 1996 and 2012, we identified 188 patients who developed recurrent pneumonia after a baseline pneumonia episode. Applying risk-set sampling at a 1:2 ratio, 353 matched controls were selected from the study cohort. We used multivariate conditional logistic regression analysis to explore the association between recurrent pneumonia and physical illness, concomitant medications, and psychotropic drugs.

Results: The findings showed that the incidence of recurrent pneumonia in BD was 6.60 cases per 100 person-years, which was higher than that in the general population. About 10% (9.24%) of cases with recurrent pneumonia died within 30 days of hospitalization. Patients had increased risk of recurrent pneumonia if they had hypertension, diabetes mellitus, cancer, or asthma. Conversely, psychotropic drugs, both first- and second-generation antipsychotics, which are known to increase susceptibility to baseline pneumonia, were not associated with risk of pneumonia recurrence.

Conclusion: We found an excess incidence of recurring pneumonia in patients with BD, and this risk was associated with pre-existing medical conditions but not psychotropic agents. Physicians should carefully consider the comorbid medical conditions of patients with BD that could lead to recurrent pneumonia.