Professor Hannah Fry, known for appearing on Celebrity Traitors, has highlighted a theory that Alzheimer's disease could "start in the nose" long before memory loss becomes obvious. Writing in her column for New Scientist, the mathematician and broadcaster discussed research suggesting the condition may have more to do with our noses than previously believed.
Fry, who lost her father to Alzheimer's in 2025, explained that the theory proposes "maybe [Alzheimer's] starts way, way, way, way, way before we thought." Experts suggest "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 get inside. She said: "One of the few areas where [the brain] has a connection to the outside is through your nose. Just behind your eyes, sitting behind your nose, there is like a little bit of your skull that is covered in tiny holes through which your olfactory nerves will dangle to give you your sense of smell."
This collection of research found that the nose could be a potential route for infection into the brain. The studies involved mice, dogs and people living in heavily polluted areas.
Studies in mice and dogs
Fry described an experiment where scientists "squirted chlamydia up their noses" in mice. She noted it was chlamydia pneumonia, "a sort of bacterial cousin of the one that gives you an STI." Within 72 hours, the mice had an infection that travelled into their brains, triggering the same kind of inflammatory response and plaques seen in brains affected by Alzheimer's.
Similar research found stray dogs in Mexican cities with severe pollution had "tiny little flecks of metals embedded inside of their brain." Fry said each fragment was "surrounded again by the same plaques, same inflammatory responses that you end up seeing in Alzheimer's."
Findings in humans
The latest research examined young children and adults who grew up in heavily polluted areas and found the same pattern. It theorised that something "sniffed up from the environment" was fought off by the brain, with the areas then surrounded by plaques and an inflammatory response commonly seen in people with Alzheimer's.
Alzheimer's disease is a progressive condition and the most common cause of dementia in the UK, according to the NHS. For help and support on navigating the condition, the Alzheimer's Society provides further information.
