Excess Deaths Attributable to Influenza-Like Illness in the ESRD Population

Abstract

Background: Morbidity and mortality vary seasonally. Timing and severity of influenza seasons contribute to those patterns, especially among vulnerable populations such as patients with ESRD. However, the extent to which influenza-like illness (ILI), a syndrome comprising a range of potentially serious respiratory tract infections, contributes to mortality in patients with ESRD has not been quantified.

Methods: We used data from the Centers for Disease Control and Prevention (CDC) Outpatient Influenza-like Illness Surveillance Network and Centers for Medicare and Medicaid Services ESRD death data from 2000 to 2013. After addressing the increasing trend in deaths due to the growing prevalent ESRD population, we calculated quarterly relative mortality compared with average third-quarter (summer) death counts. We used linear regression models to assess the relationship between ILI data and mortality, separately for quarters 4 and 1 for each influenza season, and model parameter estimates to predict seasonal mortality counts and calculate excess ILI-associated deaths.

Results: An estimated 1% absolute increase in quarterly ILI was associated with a 1.5% increase in relative mortality for quarter 4 and a 2.0% increase for quarter 1. The average number of annual deaths potentially attributable to ILI was substantial, about 1100 deaths per year.

Conclusions: We found an association between community ILI activity and seasonal variation in all-cause mortality in patients with ESRD, with ILI likely contributing to >1000 deaths annually. Surveillance efforts, such as timely reporting to the CDC of ILI activity within dialysis units during influenza season, may help focus attention on high-risk periods for this vulnerable population.

Keywords: ESRD; influenza; influenza-like illness; mortality.

Graphical abstract

Figure 1.

The intensity and timing of outpatient visits for influenza-like illness vary year to year. CDC percentage of outpatient visits for influenza-like illness. OP, outpatient.

Figure 2.

Death counts among patients with ESRD are seasonal, with higher counts during colder months. Quarterly death counts among patients with ESRD, 2000–2013.

Figure 3.

After standardizing death counts to “average summer,” the intensity and timing of death counts among patients with ESRD become apparent. Relative quarterly mortality, by quarter, compared with Q3, after accounting for death trends over time.

Figure 4.

Predicted death counts among patients with ESRD are relatively close to observed death counts. Observed versus predicted death counts in the fall (Q4) and winter (Q1) among patients with ESRD, 2000–2013.