Prevalence of Comorbid Chronic Obstructive Pulmonary Disease in Individuals Suffering from Schizophrenia and Bipolar Disorder: A Systematic Review

The disease burden associated with schizophrenia and bipolar disorder is substantial, with affected individuals having a shorter life expectancy and a high risk of severe physical comorbid conditions. These individuals are more likely to smoke and have a longer smoking history compared to the general population. Furthermore, use of antipsychotic drugs has also been linked to active smoking. Chronic obstructive pulmonary disease (COPD) is a respiratory condition affecting elderly individuals with a long smoking history, so it would be expected that individuals suffering from major mental disorders may exhibit a higher prevalence of COPD compared to the general population. We searched the databases Pubmed and Scopus for observational studies of at least 200 patients including at least one group suffering from schizophrenia or bipolar disorder and a comparison group of individuals at risk of COPD. The initial search, along with the data extraction process and the risk of bias assessment were carried out independently by the two reviewers. Eight studies were included. The risk of bias was substantial as most studies did not adequately address confounding variables. A pooled analysis showed a greater likelihood of suffering from comorbid COPD compared with the general population both for schizophrenic (OR 1.573, 1.439-1.720) and bipolar individuals (OR 1.551, 1.452-1.658). Based on these findings, COPD is more common in individuals suffering from major mental illness compared to the general population. Further research is required to ascertain whether smoking is the only cause and develop strategies for the prevention of COPD in these high-risk groups.