Every year, seasonal flu poses a serious threat to older adults, leading to higher rates of severe illness and death compared to younger people.
Now, scientists have discovered a key reason why this happens—and their findings may pave the way for new treatments to better protect the aging population.
The study, published in PNAS, found that older people produce much higher levels of a protein called apolipoprotein D (ApoD).
This protein normally plays a role in regulating fats in the body and in controlling inflammation.
But when produced at very high levels in the lungs, as happens with age, it appears to weaken the body’s ability to fight off influenza viruses.
The researchers showed that excess ApoD interferes with the immune system’s antiviral defenses, particularly type I interferons, which are critical for stopping viruses early.
Instead of helping, elevated ApoD seems to drive damaging inflammation and lung tissue injury, leaving older patients less able to resist infection and more likely to suffer serious complications.
The international research team, which included scientists from the China Agricultural University, the University of Nottingham, the University of Edinburgh, and several Chinese health institutes, used both aging-mouse models and human lung tissue samples to study the effects.
They discovered that ApoD disrupts mitochondria—the tiny structures inside cells that provide energy and also help trigger protective immune responses.
This breakdown process, known as mitophagy, leads to increased viral replication and more lung damage.
“Aging is one of the biggest risk factors for flu-related deaths,” explained Professor Kin-Chow Chang from the University of Nottingham’s School of Veterinary Medicine and Science, who co-authored the study.
“With the world’s population aging rapidly, understanding why older people are so vulnerable to flu is crucial for improving healthcare and reducing mortality.”
The identification of ApoD as a driver of severe flu in older people offers an important new target for therapy. By finding ways to block or reduce ApoD’s harmful effects, doctors may one day be able to lessen the severity of flu in the elderly.
Such treatments could significantly lower hospitalizations and deaths, especially during seasonal outbreaks or future pandemics.
Professor Chang emphasized the potential impact: “We now have an exciting opportunity to protect older patients from the worst effects of influenza by targeting ApoD. This could transform outcomes for millions of people worldwide.”
As researchers continue to explore new strategies, this discovery provides fresh hope that aging does not have to mean a higher risk of life-threatening flu. Treatments designed to curb ApoD’s harmful activity could be a game-changer for elderly patients everywhere.
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