The first signs of Alzheimer’s could hit decades before patients notice memory loss, experts have warned — in a bombshell new study that could transform the fight against Britain’s biggest killer.

Scientists say spatial awareness issues, such as struggling with a sat nav or standing awkwardly close to people, may be the earliest warning signs — striking up to 20 years before traditional symptoms like memory loss and confusion.

In a major study from Seattle, researchers examined the post-mortem brains of 84 Alzheimer’s patients and uncovered chilling evidence of early brain cell death long before damage was visible on scans.

Using powerful machine learning software, scientists tracked toxic brain proteins tau and amyloid — widely linked to the disease — and found that even low levels caused damage to key brain cells known as inhibitory neurons.

Lead author Dr Mariano Gabitto, a neuroscience professor, explained:

“Identifying the earliest neurons lost could be crucial for developing therapeutic interventions to protect them and prevent further cognitive decline.”

These vulnerable brain cells appear to be first hit in the ‘stealth phase’ of Alzheimer’s, potentially unleashing a slow cascade of cognitive collapse that spreads into the brain’s language and memory centres.

And the earlier the disease is spotted, the better chance we have of slowing it down — or even stopping it in its tracks.

Dr Igor Camargo Fontana, from the Alzheimer’s Association, said:

“The disease's long pre-symptomatic and silent period creates opportunities for early detection, early intervention and even prevention of dementia symptoms.”

It comes as dementia cases in the UK soar to nearly 1 million, with Alzheimer’s accounting for six in ten cases. Experts fear that by 2040, the number could rise to 1.4 million — piling pressure on families, the NHS, and care services.

In 2024 alone, the disease cost Britain a staggering £42 billion. That figure is expected to more than double to £90 billion within 15 years.

Campaigners are now demanding urgent investment in early detection tools, which could provide cheap and rapid screening — giving doctors a crucial head start before devastating symptoms appear.

Last year, 74,261 people died from dementia, compared to 69,178 in 2021 — making it the UK’s biggest killer.

With Alzheimer’s deaths continuing to climb, scientists are hopeful that identifying this silent phase could be the breakthrough we desperately need.