Flu-like illness contributed substantially to mortality for people with end-stage renal disease (ESRD), an analysis spanning 14 years of U.S. data indicated.
During influenza season — the 6 months from October to March — excess deaths averaged more than 1,000 annually among the at-risk ESRD population, according to David Gilbertson, PhD, of the Hennepin Healthcare Research Institute and the University of Minnesota, and colleagues, pointing to influenza-like illness (ILI) as the likely reason.
Reporting in the Journal of the American Society of Nephrology, the group calculated that a 1% absolute increase in flu-like illness during January to March — the time of year in which flu-like illness typically peaked — was tied to a 2.0% (95% CI 0.2%-3.9%) increase in relative morality during this season for patients with ESRD compared with July to September.
From October to December, which consistently had the second highest rates of illness throughout the year, a 1% absolute increase in flu-like illness was tied to a 1.5% (95% CI 0.6%-2.4%) rise in relative mortality for these patients.
“Generally speaking, during influenza/ILI seasons when influenza and ILI peaked early, more deaths occurred early, and when the illness peak was later, the peak in deaths was also later,” explained Gilbertson in a statement. “Similarly, years when influenza and ILI were particularly bad were generally years when the number of deaths was also higher than expected.”
“While ILI may not be the direct cause of death in ESRD patients, it may contribute to other causes of death; for example, patients with ILI may experience a state of acute inflammation, making them vulnerable to other infections or cardiovascular events,” he warned.
Utilizing CDC data on flu-related mortality paired with Medicare ESRD data representing 2000-2013, the researchers calculated mortality patterns broken down by season. Flu-related mortality included deaths due to illnesses defined as a fever over 100° F (37.8° C) accompanied by a cough and/or a sore throat. Although influenza is one illness under the umbrella of influenza-like illness, Gilbertson’s group pointed out several viruses can contribute to flu-like illnesses, including rhinovirus, adenovirus, respiratory syncytial virus, parainfluenza virus, and human metapneumovirus, just to name a few.
During this time period, the annual number of deaths among ESRD patients increased from around 390,000 in 2000 to nearly 680,000 in 2014, although the researchers noted this was mostly attributable to the increase in the ESRD population overall. Years that had the highest flu-related mortality included 2003-2004 and 2009-2010, whereas the least fatal flu season was 2011-2012.
ESRD patients are a particularly unique at-risk population, explained the group, not only due to a high rate of comorbidities placing them at higher risk, but also due to the combination of lowered immunologic functioning and frequent visits to maintenance hemodialysis centers, which can place them in close proximity to contagious individuals.
In order to address these concerns, Gilbertson suggested strategies could include “increased disinfection efforts in dialysis units in the winter months, and making sure all patients with kidney failure get the influenza vaccination each year.”
Despite a benefit from receiving a flu vaccine, the researchers warned nephrologists and other clinicians to “expect at most a modest benefit from any dialysis-population-wide influenza vaccination program,” as the “vaccine appears to be substantially less effective in this population.”
“[I]mmunity resulting from single dose vaccines may wane before the end of an influenza season, leading to suggestions that patients on dialysis should receive high-dose or adjuvanted influenza vaccines,” they also recommended.
The study was supported by Amgen.
Gilbertson reported no conflicts of interest. Other study authors reported several disclosures.