The impact of psychiatric disorders on chronic obstructive pulmonary disease (COPD) hospitalizations: a nationwide retrospective study

Abstract

Background: Chronic obstructive pulmonary disease (COPD) is primarily a pulmonary disease but often presents with extrapulmonary manifestations and comorbidities, including psychiatric disorders. This investigation aimed to characterize the impact of a secondary diagnosis of a broad spectrum of mental illnesses in all public COPD hospitalizations registered in Portugal from 2008 to 2015. Methods: A retrospective observational study was conducted. Hospitalization episodes of patients with at least 40 years old, discharged between 2008 and 2015 with a primary diagnosis of COPD (ICD-9-CM codes 491.x, 492.x and 496) were retrieved from a national administrative database that included all hospitalizations registered in mainland public hospitals. From these sampled episodes, secondary psychiatric diagnoses were identified and defined by the Clinical Classification Software (CCS) category codes 650-670 (excluding 662). Age at admission, sex, length of hospital stay (LoS), admission type and date, destination after discharge, in-hospital mortality, and estimated hospital charges were analyzed according to psychiatric diagnostic categories. Results: Of 66,661 COPD hospitalizations, 25,869 (38.8%) were episodes with a registered psychiatric comorbidity. These were more likely to correspond to younger inpatients (OR=2.161, 95%CI=2.094-2.231; p<0.001), to stay longer at the hospital (aOR=1.080, 95%CI=1.046-1.115; p<0.001), to incur in higher estimated charges (aOR=1.373, 95%CI=1.330-1.418; p <0.001) and to be urgently admitted (aOR=1.329, 95%CI=1.227-1.441; p<0.001). Globally, in-hospital mortality was lower for episodes with secondary psychiatric diagnoses (aOR=0.897; 95%CI=0.842-0.956; p<0.001), except for organic and neurodegenerative diseases' category and developmental disorders, intellectual disabilities and disorders usually diagnosed in infancy, childhood, or adolescence category. Discussion: These findings corroborate the additional burden placed by psychiatric disorders on COPD hospitalizations, highlighting the importance of individualizing care to address these comorbidities and minimize their impact on treatment outcomes.