Age Sways Europe’s Bloodstream Infection Rate Projections

Every year, antibiotic-resistant infections contribute to millions of deaths around the world. Age and sex can influence people’s susceptibility to these infections, but researchers do not know the extent to which these variations affect current or future trends of antibiotic-resistant infection incidence. This knowledge gap may confound their ability to intervene.

Gwenan Knight, a systems biologist at the London School of Hygiene and Tropical Medicine, wanted to better understand how demographic factors affect the rate of antibiotic-resistant infections across different populations. In a recent study, Knight and her colleagues performed computational modeling to project the incidence of bloodstream infections, including those caused by antibiotic-resistant pathogens, in Europe between 2022 and 2050.¹ Their predictions revealed an increase in infection rates among adults between ages 60 and 89, but the rates seemed to stabilize, or even decline, among younger populations. The researchers also observed that this trend was more prominent in males than females, revealing a sex-based distinction. Their findings, published in PLoS Medicine, indicate that demographic factors significantly affect the incidence of antibiotic-resistant infections.

“Our study shows that the future burden of drug-resistant infections won’t be uniform,” said Knight in a statement. “Age and sex are still rarely considered in antimicrobial resistance projections, yet they make a real difference to who is most affected.”

In a large, global-scale study, researchers previously predicted that older adults are likely at a higher risk of mortality due to antibiotic-resistant infections.² However, they projected antimicrobial resistance-related deaths, not the incidence of infections. Furthermore, while the team considered variations in age, region, and types of bacteria, they did not assess sex differences.

In the present study, Knight and her team focused only on Europe and employed a much simpler statistical model for their projections than the previous study. They analyzed publicly available data on the susceptibility of eight bacterial pathogens that commonly cause bloodstream infections to antibiotics from different European countries between 2010 and 2019. They then used these data to project the prevalence of bloodstream infections, including those caused by antibiotic-resistance microbes, through 2050. To evaluate the effects of demographic factors such as age and sex on the incidence of antibiotic-resistant infections, the researchers compared models that took these variables into consideration to those that did not.

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When the researchers did not account for age and sex, they observed that nearly half of the bacteria-antibiotic combinations showed a downward trend over time. On the other hand, models that considered the demographic factors revealed that adults aged between 60 and 89 were especially vulnerable. Furthermore, within this age group, cases were expected to increase much more steeply in males than in females. These results suggest that without considering demographic factors, researchers may severely overlook the vulnerability of certain populations and thus propose unsuitable interventions.

“This is a fantastic step forward in understanding the way that age and sex will influence the burden of drug-resistant infections in different European countries in the coming years,” said Catrin Moore, an infectious disease researcher at City St. George’s University of London and a coauthor of the study. “This [study] will help us design intervention studies focusing on the populations most at risk in the future,” she added.