Analysis of causes of death and mortality risk factors in elderly patients hospitalized due to pneumonia

Background: Many elderly patients are admitted to hospitals for pneumonia, and the mortality rate for such cases is high. However, few studies have analyzed in detail the causes of death in the elderly hospitalized due to pneumonia. Purpose: The study aimed to investigate the prognosis of elderly individuals hospitalized due to pneumonia from the viewpoints of mortality risk factors and causes of death. Methods: The subjects were patients aged 70 years or older who were admitted to our hospital for pneumonia from January 2015 to June 2017. A total of 442 cases (mean age; 83.1 years) were targeted for analysis after excluding patients with hospital-acquired pneumonia, patients who were transferred to another facility. A total of 58 patients died in the hospital. In addition to analyzing their causes of death, the following factors were compared with cases that showed improvement: altered mental status; blood pressure; saturation of oxygen (SpO₂); age; length of hospital stay; body mass index (BMI); serum albumin (ALB) levels; serum urea nitrogen (UN) levels; serum C-reactive protein (CRP) levels. Results: The causes of death in the 58 patients were as follows: pneumonia (15 cases; 26%), frailty (12 cases; 21%), heart failure (7 cases; 12%), sepsis (5 cases; 9%), lung cancer (6 cases; 10%), non-lung cancers (4 cases), and other causes (9 cases). A logistic regression analysis revealed that BMI (OR 0.88; 95% CI: 0.8-0.97), altered mental status (2.23, 1.16–4.30), SpO₂≤90% (2.16, 1.08–4.33), and ALB levels (0.34, 0.19–0.61) were independent mortality risk factors. Conclusions: It is insufficient to categorize pneumonia in elderly patients as simply an infectious disease.