Infectious diseases are the leading cause of deaths in adults aged 65 years or older. Studies of adverse infection outcomes have been limited to specific infections and acute episodes and have not investigated longitudinal trends of cumulative infections. We aimed to identify distinct trajectories of longitudinal infection episodes in older adults and to assess their corresponding risk of all-cause mortality.
In this retrospective cohort study, we included people aged 65 years or older who were admitted to hospital between Jan 1 and Dec 31, 2011, with one of the following infections: urinary tract, pneumonia, sepsis, cellulitis, cholecystitis, peritonitis, endocarditis, and meningitis. Participants were identified from Taiwan’s National Health Insurance Research Database. We analysed infection episodes on a quarterly basis during a 5-year period (2011-15) and used group-based trajectory modelling to identify distinct trajectories. We examined the associations between infection trajectories and all-cause mortality using Kaplan-Meier curves and the Cox proportional hazard model.
Among 79 666 eligible older adults, we identified four distinct infection trajectories over the 5-year follow-up: infrequent (58 619 [73·6%]), increasing (9746 [12·2%]), decreasing (9069 [11·4%]), and frequent (2232 [2·8%]). Compared with people with infrequent infections, the adjusted hazard ratios for all-cause mortality were 2·96 (95% CI 2·82-3·11) in participants with frequent infections, 2·15 (2·09-2·22) in those with increasing infections, and 1·85 (1·80-1·91) in those with decreasing infections.
Older adults with multiple infection episodes, irrespective of type, pathogens, and distinct infection pattern, had greater risk of all-cause mortality compared with those with infrequent infections. Further research to define the overall infection burden in older adults is needed for risk stratification and to inform prevention strategies.
The Interdisciplinary Research Center for Healthy Longevity of National Yang Ming Chiao Tung University from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education, the National Science and Technology Council, and the Ministry of Science and Technology in Taiwan.

Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.