The incidence and all-cause mortality of pneumonia in patients with schizophrenia: a nine-year follow-up study

Objective: This study sought to estimate the incidence, all-cause mortality and relative risks for patients with schizophrenia after a pneumonia diagnosis.

Methods: The population was identified from the Taiwanese National Health Insurance Research Database (NHIRD) in 1999 and included 59,021 patients with schizophrenia and 236,084 age- and sex-matched control participants without schizophrenia. These participants were randomly selected from the 23,981,020-participant NHIRD, which contain 96% of the entire population. Using the 2000-2008 NIHRD, the incidence and nine-year pneumonia-free survival rate of pneumonia (ICD-9-CM codes 486 and 507.0-507.8) were calculated.

Results: Over nine years, 6055 (10.26%) patients with schizophrenia and 7844 (3.32%) controls had pneumonia. The pneumonia incidence density was 11.4/1000 person-years among the patients with schizophrenia, who experienced a 3.09-fold increased risk of developing pneumonia. After adjusting for other covariates, the patients with schizophrenia still experienced a 1.77-fold increased risk of developing pneumonia. Although, without adjustment, fewer schizophrenia patients than controls died after having pneumonia (2121 [35.12%] vs. 3497 [44.62%]), after adjusting for other variables, the mortality hazard ratio for patients with schizophrenia was 1.39.

Conclusions: During a nine-year follow-up, the likelihood of developing pneumonia and all-cause mortality among patients with schizophrenia was higher than that of the non-schizophrenia group as was the mortality rate. Interestingly, the psychiatric proportion of days covered (PDC) was positively associated with pneumonia (OR: 2.51) but negatively associated with death (HR: 0.72). These findings imply the importance of iatrogenic factors and psychotropic drugs (including their benefits and side effects) and highlight the directions for future studies.