title: Epidemiology and long-term clinical and biologic risk factors for pneumonia in community-dwelling older Americans: analysis of three cohorts.
abstract: BACKGROUND
  Preventing pneumonia requires better understanding of incidence, mortality, and long-term clinical and biologic risk factors, particularly in younger individuals.
  
  
  METHODS
  This was a cohort study in three population-based cohorts of community-dwelling individuals. A derivation cohort (n = 16,260) was used to determine incidence and survival and develop a risk prediction model. The prediction model was validated in two cohorts (n = 8,495). The primary outcome was 10-year risk of pneumonia hospitalization.
  
  
  RESULTS
  The crude and age-adjusted incidences of pneumonia were 6.71 and 9.43 cases/1,000 person-years (10-year risk was 6.15%). The 30-day and 1-year mortality were 16.5% and 31.5%. Although age was the most important risk factor (range of crude incidence rates, 1.69-39.13 cases/1,000 person-years for each 5-year increment from 45-85 years), 38% of pneumonia cases occurred in adults &lt; 65 years of age. The 30-day and 1-year mortality were 12.5% and 25.7% in those &lt; 65 years of age. Although most comorbidities were associated with higher risk of pneumonia, reduced lung function was the most important risk factor (relative risk = 6.61 for severe reduction based on FEV1 by spirometry). A clinical risk prediction model based on age, smoking, and lung function predicted 10-year risk (area under curve [AUC] = 0.77 and Hosmer-Lemeshow [HL] C statistic = 0.12). Model discrimination and calibration were similar in the internal validation cohort (AUC = 0.77; HL C statistic, 0.65) but lower in the external validation cohort (AUC = 0.62; HL C statistic, 0.45). The model also calibrated well in blacks and younger adults. C-reactive protein and IL-6 were associated with higher pneumonia risk but did not improve model performance.
  
  
  CONCLUSIONS
  Pneumonia hospitalization is common and associated with high mortality, even in younger healthy adults. Long-term risk of pneumonia can be predicted in community-dwelling adults with a simple clinical risk prediction model.
authors.affiliation: Clinical Research, Investigation, and Systems Modeling of Acute Illness (CRISMA) Center, University of Pittsburgh, Pittsburgh, PA; Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA. Electronic address: yendes@upmc.edu.
authors.forename: Sachin
authors.initials: S
authors.lastname: Yende
authors.affiliation: Clinical Research, Investigation, and Systems Modeling of Acute Illness (CRISMA) Center, University of Pittsburgh, Pittsburgh, PA; Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Karina
authors.initials: K
authors.lastname: Alvarez
authors.affiliation: Department of Epidemiology, UNC Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Laura
authors.initials: L
authors.lastname: Loehr
authors.affiliation: School of Public Health, University of Minnesota, Minneapolis, MN.
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Folsom
authors.affiliation: Department of Epidemiology, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.affiliation: Clinical Research, Investigation, and Systems Modeling of Acute Illness (CRISMA) Center, University of Pittsburgh, Pittsburgh, PA; Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Weissfeld
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Wunderink
authors.affiliation: The Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, NC.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Kritchevsky
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Mukamal
authors.affiliation: Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC.
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: London
authors.affiliation: Laboratory of Epidemiology, Demography, and Biometry, National Institute on Aging, Bethesda, MD.
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.affiliation: Departments of Medicine and Epidemiology and Biostatistics, University of California, San Francisco, CA.
authors.forename: Doug C
authors.initials: DC
authors.lastname: Bauer
authors.affiliation: Clinical Research, Investigation, and Systems Modeling of Acute Illness (CRISMA) Center, University of Pittsburgh, Pittsburgh, PA; Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Derek C
authors.initials: DC
authors.lastname: Angus
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017714:Community-Acquired Infections / Q000453:epidemiology*; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology*; D011379:Prognosis; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D015996:Survival Rate / Q000639:trends; D013997:Time Factors