Etiology, Clinical Course, and Outcomes of Pneumonia in the Elderly: A Retrospective and Prospective Cohort Study in Thailand

Mayada Osman,Udomsak Silachamroon,Supitcha Kamolratanakul,Weerawat Manosuthi,Punnee Pitisuttithum,Chayasin Mansanguan,Jaranit Kaewkungwal

doi:10.4269/ajtmh.20-1393

Abstract

.Pneumonia is a leading cause of hospitalization and death among elderly adults. We performed a retrospective and prospective observational study to describe the etiology, clinical course, and outcomes of pneumonia for patients 60 years and older in Thailand. We enrolled 490 patients; 440 patients were included in the retrospective study and 50 patients were included in the prospective study. The CURB-65 score and a modified SMART-COP score (SMART-CO score) were used to assess disease severity. The median patient age was 80 years (interquartile range, 70–87 years); 51.2% were men. Klebsiella pneumoniae (20.4%) and Pseudomonas aeruginosa (15.5%) were the most common causative agents of pneumonia. A significant minority (23%) of patients were admitted to the intensive care unit (ICU), and mortality among this subset of patients was 45%. Most patients (80.8%) survived and were discharged from the hospital. The median duration of hospitalization was 8 days (interquartile range, 4–16 days). In contrast, 17.6% of patients died while undergoing care and 30-day mortality was 14%. Factors significantly associated with mortality were advanced age (P = 0.004), male sex (P = 0.005), multiple bacterial infections (P = 0.007; relative risk [RR], 1.88; 95% confidence interval [CI], 1.19–2.79), infection with multi-drug-resistant/extended-spectrum B-lactamase-producing organisms (P < 0.001; RR, 2.82; 95% CI, 1.83–4.85), ICU admission (P < 0.001; RR, 1.8; 95% CI, 1.4–2.3), and complications of pneumonia (P < 0.001; RR, 2.5; 95% CI, 1.8–3.4). Patients with higher SMART-CO and CURB-65 scores had higher rates of ICU admission and higher 30-day mortality rates (P < 0.001). These results emphasize the importance of Gram-negative bacteria, particularly K. pneumoniae and P. aeruginosa, as major causes of pneumonia among the elderly in contrast to other reports, Streptococcus pneumoniae is a common cause of pneumonia among elderly individuals worldwide. The SMART-COP and CURB-65 scores were developed to assess pneumonia severity and predict mortality of young adults with pneumonia. Few studies have examined the appropriateness of these scores for elderly patients with multiple comorbidities. A limited number of studies have used modified versions of these scores among elderly individuals. We found that Gram-negative bacteria has a major role in the etiology of pneumonia among elderly individuals in Southeast Asia. A significant proportion of elderly individuals with low CURB-65 scores were admitted to the hospital, indicating that hospital admission may reflect fragility among elderly individuals with low CURB-65 scores. The modified SMART-COP score (SMART-CO score) sufficiently predicted intensive care unit admission and the need for intensive vasopressor or respiratory support. A SMART-CO score ≥ 7 accurately predicted 30-day mortality.

Highlights

Pneumonia is one of the most common infectious diseases in clinical practice and a frequent cause of hospital admission and mortality worldwide
Factors significantly associated with mortality were advanced age (P = 0.004), male sex (P = 0.005), multiple bacterial infections (P = 0.007; relative risk [RR], 1.88; 95% confidence interval [CI], 1.19–2.79), infection with multi-drugresistant/extended-spectrum B-lactamase-producing organisms (P < 0.001; RR, 2.82; 95% CI, 1.83–4.85), intensive care unit (ICU) admission (P < 0.001; RR, 1.8; 95% CI, 1.4–2.3), and complications of pneumonia (P < 0.001; RR, 2.5; 95% CI, 1.8–3.4)
Patients with higher SMART-CO and CURB-65 scores had higher rates of ICU admission and higher 30-day mortality rates (P < 0.001). These results emphasize the importance of Gram-negative bacteria, K. pneumoniae and P. aeruginosa, as major causes of pneumonia among the elderly in contrast to other reports, Streptococcus pneumoniae is a common cause of pneumonia among elderly individuals worldwide

Summary

Introduction

Pneumonia is one of the most common infectious diseases in clinical practice and a frequent cause of hospital admission and mortality worldwide. Factors such as weakened or suppressed immunity, comorbidities, diminished cough reflex, and poor functional status contribute to the increased incidence of pneumonia compared with that of younger adults.[1,2]. The presentation, etiology, clinical course, and outcomes of pneumonia may differ compared with those of younger adults. The etiological agents causing pneumonia in elderly patients vary geographically.[3,4,5] Streptococcus pneumoniae is the most common cause of community-acquired pneumonia (CAP) in Western European countries[6] and developing countries.[7,8] In contrast, in others Asian countries, Gram-negative bacteria are common causes of pneumonia among the elderly and result in high mortality rates.[2,9] For many elderly patients with pneumonia, the etiological agent is difficult to identify because of their inability to expectorate or use of empiric antimicrobial therapy

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