Risk factors for pneumonia in patients with schizophrenia

Pneumonia is a major cause of death in patients with schizophrenia. Preventive strategies based on identifying the risk factors are needed to reduce pneumonia-related mortality. This study aimed to clarify the risk factors for pneumonia in patients with schizophrenia.

We retrospectively reviewed the clinical files of consecutive patients with schizophrenia admitted to Tokyo Metropolitan Matsuzawa Hospital during a four-year period from January 2014 to December 2017. We analyzed the clinical differences between patients with and without pneumonia.

Of the 2209 patients enrolled, 101 (4.6%) received the diagnosis of pneumonia at the time of hospital admission while 2108 (95.4%) did not have pneumonia. Multivariable analysis to determine the risk factors related to pneumonia showed that the use of atypical antipsychotics had the highest odds ratio among the predictive factors (2.7; 95% confidence interval [CI] 1.0-17.7; P = 0.046), followed by a total chlorpromazine equivalent dose ≥600 mg (2.6; 95% CI 1.7-4.0; P < 0.001), body mass index <18.5 kg/m² (2.3; 95% CI 1.6-3.6; P < 0.001), smoking history (2.0; 95% CI 1.3-3.1; P < 0.001), and age ≥50 years (1.7; 95% CI 1.2-2.6; P = 0.002).

We found that advanced age, underweight, smoking habit, use of atypical antipsychotics, and large doses of antipsychotics were risk factors for pneumonia in patients with schizophrenia. Among these factors, it was unclear whether the use of antipsychotics was a direct cause of pneumonia due to is uncertain because our retrospective study design. However, our result might be a good basis of further study focused on reducing pneumonia-related fatalities in schizophrenic patients with pneumonia.