Date of Award

January 2015

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

James L. Hadler


BACKGROUND: Previous studies have shown sex differences in influenza hospitalizations, but sex differences across the United States by demographic characteristics have not been well-established. We investigated potential sex differences across 14 FluSurv-NET (FSN) sites that conduct active population-based surveillance for laboratory-confirmed influenza-associated hospitalizations among residents of 76 counties in 2010-2012, stratifying by age, race, and census tract-level poverty.

METHODS: We used 6,292 laboratory-confirmed adult (>18 years) cases collected by the 14 FSN sites during the 2010-11 and 2011-12 influenza seasons linked to 2010 Census data to calculate overall age-adjusted and age-specific incidence and incidence rate ratios (IRRs) for sex by four race/ethnic and four census-tract poverty (SES) categories. Analyses were repeated excluding pregnant women, with denominator pregnancy adjustments calculated by subtracting the percentage of women 18-49 years old with live births in 2010.

RESULTS: Overall, 55.5% of cases were female. Females were more likely to be hospitalized than males (IRR 1.17, 95% CI 1.11-1.22), but this difference did not remain after age adjustment. Females at highest risk were 18-49 years old (IRR 1.32, 95% 1.20-1.44), which was fully accounted for by pregnancy. Females were at lower risk in the ≥85 year old category (IRR 0.67, 95% CI 0.59-0.77). IRRs varied by race and SES, but in no SES group was the aIRR significantly greater than 1. White females were less likely to be hospitalized than white males (aIRR 0.91, 95% CI 0.85-0.98) while Hispanic females were more likely to be hospitalized than Hispanic males (aIRR 1.25, 95% CI 1.06-1.44). Of the 14 sites examined, 12 had crude incidence rate ratios greater than 1, but none were significant after age adjustment.

CONCLUSIONS: In 2010-2012, there were sex differences in influenza-associated hospitalizations that were highly dependent upon age, but varied by race/ethnicity and US site. Further research is needed to understand the drivers behind these differences, and analysis of data from different years is needed to determine the consistency of these findings.


This is an Open Access Thesis.