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

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  • 1 Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand;
  • 2 Department of Medicine, Bamrasnaradura Infectious Diseases Institute, Nonthaburi, Thailand

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. 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.

Author Notes

Financial support: This study was funded by Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. The funder had no role in the study design, decision to publish, or preparation of the manuscript.

Authors’ addresses: Mayada Osman, Jaranit Kaewkungwal, Udomsak Silachamroon, Chayasin Mansanguan, Supitcha Kamolratanakul, and Punnee Pitisuttithum, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand, E-mails: mayada200623@yahoo.com, jaranit.kae@mahidol.ac.th, udomsak.sil@mahidol.ac.th, chayasin.man@mahidol.ac.th, ksupitcha@hotmail.com, and punnee.pit@mahidol.ac.th. Weerawat Manosuthi, Department of Medicine, Bamrasnaradura Infectious Diseases Institute, Nonthaburi, Thailand, E-mail: idweerawat@yahoo.com.

Address correspondence to Punnee Pitisuttithum, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Road, Ratchathewi, Bangkok 10400, Thailand. E-mail: punnee.pit@mahidol.ac.th

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