Professor Hannah Fry has highlighted a theory that Alzheimer's disease could begin in the nose, potentially years before any memory loss becomes apparent. Writing in her column for New Scientist, the mathematician and Celebrity Traitors star explained that emerging research suggests the condition may be far more closely linked to the nose than specialists previously believed.
Fry, who lost her father to Alzheimer's in 2025, said the theory proposes that the disease "starts way, way, way, way, way before we thought" and that "this isn't just something that goes wrong in your brain."
The Nose as a Route to the Brain
In an Instagram video, Fry described how the brain is "locked away" inside the skull, with very little able to gain entry. She noted that one of the few connections to the outside is through the nose, where a small area of the skull behind the eyes is covered in tiny holes through which olfactory nerves dangle to provide the sense of smell.
This collection of research identified that the nose could represent a potential pathway for infection into the brain. The studies involved mice, dogs, and people living in heavily polluted areas.
Evidence from Mice and Dogs
Fry detailed an experiment in which scientists squirted chlamydia pneumonia, a bacterial cousin of the strain that causes an STI, up the noses of mice. Within 72 hours, the infection had travelled into their brains and triggered the same kind of inflammatory response and plaques seen in brains riddled with Alzheimer's.
Similar research found that stray dogs in Mexico living in cities with severe pollution had "tiny little flecks of metals embedded inside of their brain." Fry said each fragment was surrounded by the same plaques and inflammatory responses seen in Alzheimer's.
Findings in Humans
The most recent research has examined young children and adults raised in heavily polluted areas and identified the same pattern. It suggested that something "sniffed up from the environment" was fought off by the brain, with the affected areas subsequently surrounded by plaques and an inflammatory response commonly observed in those with Alzheimer's.
Alzheimer's disease is a progressive condition and the most common cause of dementia in the UK, according to the NHS.
