February 15, 2016
1 min read

Socioeconomic status influences risk for influenza hospitalization

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The incidence of influenza hospitalizations appeared to be greater within poorer regions of the United States, according to recent MMWR data.

Previous studies analyzing hospitalization by poverty level have described this effect, the CDC researchers wrote, although these were often limited by geographically small catchment areas. To expand the scope of such analyses, the researchers examined data collected from 14 sites participating in the Influenza Hospitalization Surveillance Network (FluSurv-NET) during the 2011-2012 and 2012-2013 influenza seasons. This sample, which included 78 counties and represented approximately 9% of the national population, was assigned to individual census tracts and categorized by the proportion of households living below the federal poverty level. After adjusting for age, researchers observed overall incidence among the census tracts for any potential interactions.

There were 7,936 influenza-related hospitalizations coded and included in analyses. The overall age-adjusted incidence in areas where more than 20% of persons lived in poverty (high poverty) was 21.5 per 100,000 persons (95% CI, 20.7-22.4), while areas where less than 5% lived in poverty (low poverty) was 10.9 (95% CI, 10.3-11.4). This relationship was consistent across all site and demographics, as well as when individually examining hospitalizations requiring intensive care (incidence rate ratio = 1.96; 95% CI, 1.7-2.3), hospitalizations requiring mechanical ventilation (IRR = 2.03; 95% CI, 1.6-2.5) and for deaths occurring within 30 days of hospitalization (IRR = 1.82; 95% CI, 1.3-2.7). Also of note was the portion of hospitalized patients who were vaccinated, which the researchers said ranged from 48% in low poverty tracts to 35% in high poverty tracts.

“The association of higher census tract-level poverty with higher influenza-related hospitalization rates appears to be robust, occurring across counties in 14 states, within pediatric and adult age groups, and across racial/ethnic groups,” the researchers wrote. “Possible contributing factors are lower vaccination rates in residents of poorer census tracts, poverty-related crowding with higher rates of influenza transmission, and higher prevalence of medical conditions predisposing persons to influenza complications in poorer areas.” – by Dave Muoio

Disclosure: The researchers report no relevant financial disclosures.