title: Improving the estimation of influenza-related mortality over a seasonal baseline.
abstract: BACKGROUND
  Existing methods for estimation of mortality attributable to influenza are limited by methodological and data uncertainty. We have used proxies for disease incidence of the three influenza cocirculating subtypes (A/H3N2, A/H1N1, and B) that combine data on influenza-like illness consultations and respiratory specimen testing to estimate influenza-associated mortality in the United States between 1997 and 2007.
  
  
  METHODS
  Weekly mortality rate for several mortality causes potentially affected by influenza was regressed linearly against subtype-specific influenza incidence proxies, adjusting for temporal trend and seasonal baseline, modeled by periodic cubic splines.
  
  
  RESULTS
  Average annual influenza-associated mortality rates per 100,000 individuals were estimated for the following underlying causes of death: for pneumonia and influenza, 1.73 (95% confidence interval = 1.53-1.93); for chronic lower respiratory disease, 1.70 (1.48-1.93); for all respiratory causes, 3.58 (3.04-4.14); for myocardial infarctions, 1.02 (0.85-1.2); for ischemic heart disease, 2.7 (2.23-3.16); for heart disease, 3.82 (3.21-4.4); for cerebrovascular deaths, 0.65 (0.51-0.78); for all circulatory causes, 4.6 (3.79-5.39); for cancer, 0.87 (0.68-1.05); for diabetes, 0.33 (0.26-0.39); for renal disease, 0.19 (0.14-0.24); for Alzheimer disease, 0.41 (0.3-0.52); and for all causes, 11.92 (10.17-13.67). For several underlying causes of death, baseline mortality rates changed after the introduction of the pneumococcal conjugate vaccine.
  
  
  CONCLUSIONS
  The proposed methodology establishes a linear relation between influenza incidence proxies and excess mortality, rendering temporally consistent model fits, and allowing for the assessment of related epidemiologic phenomena such as changes in mortality baselines.
authors.affiliation: Department of Epidemiology, Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, MA 02115, USA. egoldste@hsph.harvard.edu
authors.forename: Edward
authors.initials: E
authors.lastname: Goldstein
authors.forename: Cecile
authors.initials: C
authors.lastname: Viboud
authors.forename: Vivek
authors.initials: V
authors.lastname: Charu
authors.forename: Marc
authors.initials: M
authors.lastname: Lipsitch
mesh_terms: D000544:Alzheimer Disease / Q000453:epidemiology; D002318:Cardiovascular Diseases / Q000453:epidemiology; D002423:Cause of Death; D015897:Comorbidity; D003920:Diabetes Mellitus / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000145:classification / Q000401:mortality* / Q000517:prevention & control; D007674:Kidney Diseases / Q000453:epidemiology; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology; D012044:Regression Analysis; D012140:Respiratory Tract Diseases / Q000453:epidemiology; D012621:Seasons; D014481:United States / Q000453:epidemiology
chemical_list: D007252:Influenza Vaccines