Use of population-based cohort data to assess community-acquired pneumonia: a powerful approach.

Received 26 August 2004; accepted 30 August 2004; electronically published 8 November 2004. Correspondence: Dr. Marie R. Griffin, A-1110 Medical Center North, 1161 21st Ave. S, Nashville, TN 37232 (marie.griffin@vanderbilt.edu). Clinical Infectious Diseases 2004; 39:1651–3 2004 by the Infectious Diseases Society of America. All rights reserved. 1058-4838/2004/3911-0015$15.00 Understanding the epidemiology of a disease is essential to designing optimal strategies for diagnosis, prevention, and treatment. Nowhere is this truer than for pneumonia. There are few estimates of the true burden of community-acquired pneumonia (CAP), especially in subsets of patients defined by age and risk group. Application of definitive diagnostic evaluations to large, diverse populations to measure pneumonia incidence is not practical. However, the development of solid case definitions and their application to population-based data from large, linked databases facilitates measurement of the pneumonia disease burden and movement toward disease control strategies. Linked information systems, including microbiologic surveillance data, private and public vaccination records, and administrative health data, are a powerful population-based resource for investigations of disease incidence and of the impact of specific interventions, such as the introduction of vaccines or targeted educational programs. The study in this issue of Clinical Infectious Diseases by Jackson et al. [2] illustrates the power of using such data for detailed descriptions of the epidemiology of a common problem, CAP, in an important demographic group, seniors aged 65 years. With use of health maintenance organization data from 46,000 seniors in Washington State with 1122,000 person-years of observation, Jackson et al. [2] defined hospitalized episodes of CAP using specific International Classification of Diseases, Ninth Revision, Clinical Modification codes for pneumonia coupled with the requirement of a clinical diagnosis of pneumonia. The definition of pneumonia in outpatients also required that the patient both underwent chest radiography and was given a prescription of antibiotics within 14 days after onset of the pneumonia episode. The authors identified 12400 hospitalizations and 3100 outpatient encounters for presumptive pneumonia, reviewed an impressive 97% of medical charts, and confirmed that 60%– 70% of subjects had CAP. Rates of pneumonia were higher in men and older seniors, with 1 in 20 persons aged 85 years developing pneumonia annually. More than 12% of persons who were hospitalized with pneumonia died within 30 days after hospital admission. Markers of comorbid illness, such as underlying malignancy, preexisting pulmonary disease, and increased use of health care services (including home oxygen), were independently associated with increased risks of both CAP and hospitalization. This study provides important comprehensive population-based data on the incidence of CAP in a growing segment of the population: noninstitutionalized seniors. The majority (59.3%) of episodes of pneumonia in the study population were treated in the outpatient setting. Omission of these cases in any description of the epidemiology of CAP would overestimate the impact of chronic comorbid illnesses on overall pneumonia rates and underestimate the burden of disease. Another useful feature of such cohort studies is the ability to provide population-based assessments of the “attributable risk” for specific conditions—how much

[1]  A. Falsey,et al.  Respiratory Syncytial Virus Infection in Adults , 2005, Clinical microbiology reviews.

[2]  W. Thompson,et al.  The Burden of Community-Acquired Pneumonia in Seniors: Results of a Population-Based Study , 2004, Clinical infectious diseases : an official publication of the Infectious Diseases Society of America.

[3]  Shabir A Madhi,et al.  A role for Streptococcus pneumoniae in virus-associated pneumonia , 2004, Nature Medicine.

[4]  Derick R. Peterson,et al.  Risk factors for severe respiratory syncytial virus infection in elderly persons. , 2004, The Journal of infectious diseases.

[5]  K. Edwards,et al.  Winter viruses: influenza- and respiratory syncytial virus-related morbidity in chronic lung disease. , 2002, Archives of internal medicine.

[6]  R. Dittus,et al.  Influenza– and Respiratory Syncytial Virus–Associated Morbidity and Mortality in the Nursing Home Population , 2003, Journal of the American Geriatrics Society.

[7]  J. McCullers,et al.  Role of neuraminidase in lethal synergism between influenza virus and Streptococcus pneumoniae. , 2003, The Journal of infectious diseases.

[8]  D. Fleming,et al.  Contribution of influenza and respiratory syncytial virus to community cases of influenza-like illness: an observational study , 2001, The Lancet.

[9]  L. Simonsen,et al.  The Japanese experience with vaccinating schoolchildren against influenza. , 2001, The New England journal of medicine.

[10]  C L Bartlett,et al.  Risk factors for community-acquired pneumonia diagnosed upon hospital admission. British Thoracic Society Pneumonia Study Group. , 2000, Respiratory medicine.

[11]  C. González,et al.  Proportion of community-acquired pneumonia cases attributable to tobacco smoking. , 1999, Chest.

[12]  A. Falsey Respiratory syncytial virus infection in older persons. , 1998, Vaccine.

[13]  MD Janet A. Englund,et al.  Respiratory Viral Infections in Immunocompetent and Immunocompromised Persons , 1997, The American Journal of Medicine.

[14]  Recommendations for influenza immunization of children. , 2004, Pediatrics.

[15]  Update: influenza-associated deaths reported among children aged <18 years--United States, 2003-04 influenza season. , 2004, The Annals of pharmacotherapy.

[16]  M. Kolczak,et al.  Cigarette smoking and invasive pneumococcal disease. Active Bacterial Core Surveillance Team. , 2000, The New England journal of medicine.