Association of age and comorbidity on 2009 influenza A pandemic H1N1-related intensive care unit stay in Massachusetts

Am J Public Health. 2014 Nov;104(11):e118-25. doi: 10.2105/AJPH.2014.302197. Epub 2014 Sep 11.


Objectives: We compared comorbidity measures by age group and risk factors for influenza-like illness (ILI)-related intensive care unit (ICU) stay during the 2009 seasonal influenza and influenza A (pH1N1) pandemic.

Methods: We identified all patients discharged from Massachusetts hospitals with ILI-related diagnoses between October 1, 2008, and April 25, 2009, and pH1N1-related diagnoses between April 26 and September 30, 2009. We calculated the Diagnostic Cost Group (DxCG) risk score as a measure of comorbidity. We used logistic regression predictive models to compare ICU stay predictors.

Results: Mean DxCG scores were similar for pH1N1 and seasonal influenza time periods (0.69 and 0.70). Compared with those aged 45 to 64 years, patients younger than 5, 5 to 12, and 13 to 18 years had an increased risk of pH1N1-related ICU stay. Within the pH1N1 cohort, an asthma diagnosis was highly predictive of ICU admission among those younger than 5, 5 to 12, and 13 to 18 years, and pregnancy among those aged 26 to 44 years.

Conclusion: High-risk groups, including children with asthma or pregnant women, would benefit from improved surveillance and resource allocation during influenza outbreaks to prevent serious ILI-related complications.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Asthma / epidemiology
  • Child
  • Child, Preschool
  • Comorbidity
  • Female
  • Humans
  • Influenza A Virus, H1N1 Subtype*
  • Influenza, Human / epidemiology*
  • Intensive Care Units / statistics & numerical data*
  • Logistic Models
  • Massachusetts / epidemiology
  • Middle Aged
  • Pandemics / statistics & numerical data*
  • Pregnancy
  • Pregnancy Complications, Infectious / epidemiology
  • Risk Factors
  • Young Adult