Alzheimer's Theory Points to the Nose as Origin
Early animal and pollution studies suggest a nasal infection route, though the link to human disease is not yet proven.
Updated on Nov. 3, 2026 in Alzheimer’s
Mathematician and broadcaster Hannah Fry has promoted a theory that Alzheimer's disease could begin in the nose, drawing on early animal and environmental research. The idea was shared in her New Scientist column and an Instagram video, and it is not yet an established finding. Readers following Alzheimer's research worldwide should treat it as a hypothesis under study.
Why it matters
Alzheimer's is the most common cause of dementia, and identifying how the disease starts could eventually shape prevention and early intervention. The theory links a possible infection route and airborne pollution exposure to brain changes, which is why researchers are paying attention. Fry's personal connection, after her father died of Alzheimer's in 2025, has also brought the question to a wide audience.
The nose-to-brain idea rests mainly on a mouse infection experiment and a study of stray dogs in polluted Mexican cities, with a similar pattern reported in some people living in heavily polluted areas. These are preliminary observations, and the results do not yet establish a causal link to Alzheimer's in humans.
The players
Hannah Fry
Mathematician and broadcaster who has promoted the nose-origin theory of Alzheimer's in her New Scientist column and an Instagram video.
The details
The olfactory nerves that carry smell signals pass through tiny openings in the skull behind the eyes and nose, a route that could in principle let microbes or particles reach the brain. In the mouse study, researchers squirted chlamydia pneumonia up the animals' noses and found it spread to the brain within 72 hours, where it triggered inflammation and plaques resembling those seen in Alzheimer's. In stray dogs living with heavy air pollution, researchers found metal fragments embedded in brain tissue, each surrounded by plaques and inflammatory responses similar to those in Alzheimer's.
Timeline
2025: Hannah Fry's father died of Alzheimer's disease.
3 November 2026: An article on the nose-Alzheimer's theory was published.
Health Landscape
Alzheimer's is a progressive condition and the most common cause of dementia in the UK, according to the NHS, and current research focuses largely on its biological and genetic drivers. A nasal-origin theory, if confirmed, would add environmental and infectious factors to that picture, but it remains a hypothesis at the animal and observational stage.
The nose-origin idea is not yet a basis for changing screening, prevention, or treatment decisions. If you have questions about memory changes or family history of dementia, it is worth discussing them with your doctor rather than acting on this theory alone.
The takeaway
The nose-to-brain theory is an interesting hypothesis but remains unproven in people. If memory concerns arise, talk with a physician about assessment and support rather than changing habits based on this idea alone.
Further reading
For the wider context on how the disease develops, see our Alzheimer’s coverage.
More information
Find trusted support and information from the Alzheimer’s Society.
