Dementia is a group of symptoms related to the ongoing decline of the brain. And Alzheiemer’s disease is the most common type of dementia.

Many of us are aware of some of the most well-known signs of Alzheimer’s, with memory loss being one of them.

However, new research has found a certain warning sign that could appear more than two decades before memory loss even starts.

A trial showed that poor spatial navigation could indicate the disease 25 years earlier than symptoms could usually begin.

Scientists say this could ensure the earliest possible diagnosis of the disease – crucial for treatment as well as research into possible prevention.

As part of the study, which was published in the Alzheimer’s and Dementia journal, researchers from University College London (UCL) asked a group of 100 people to navigate a virtual reality environment while wearing VR headsets.

Participants, aged between 43 and 66, were all judged to be predisposed to Alzheimer’s.

This was either because they had family history of the disease, they had the APOE-ε4 allele gene associated with a heightened risk of the disease, or engaged in lifestyle risk factors such as low levels of exercise.

But they were all asymptomatic, meaning they were showing no signs of Alzheimer’s.

They were also all around 25 years younger than their medically estimated age of the onset of dementia.

Results of the study showed that people at a greater risk of developing Alzheimer’s were “impaired” on the VR navigation task.

However, they did not have a corresponding impairment on other cognitive tests, such as those surrounding memory, suggesting that poor spatial navigation may develop years or decades before the onset of other symptoms.

First author Dr Coco Newton said: “Our results indicated that this type of navigation behaviour change might represent the very earliest diagnostic signal in the Alzheimer’s disease continuum – when people move from being unimpaired to showing manifestation of the disease.

“We are now taking these findings forward to develop a diagnostic clinical decision support tool for the NHS in the coming years, which is a completely new way of approaching diagnostics and will hopefully help people to get a more timely and accurate diagnosis.”

Study leader Professor Dennis Chan added: “We are excited by these findings for two main reasons.

“First, they improve detection of the clinical onset of Alzheimer’s disease, which is critical for prompt application of treatments.

“Second, the VR navigation test is based on our knowledge of the spatial properties of cells in the brain’s temporal lobe and the application of cellular neuroscience to clinical populations helps bridge the gap in understanding how disease at the neuronal level can result in the clinical manifestation of disease.

“This knowledge gap currently represents one of the biggest barriers to progress in Alzheimer’s research.”

The research also found that the spatial navigation impairment was observed more strongly in men than in women.

“This highlights the need for further study of the differing vulnerability of men and women to Alzheimer’s disease, and the importance of taking gender into account for both diagnosis and future treatment,” Prof Chan said.

Meanwhile, Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, commented: “One in three people born today will go on to develop dementia, and early and accurate diagnosis of the diseases that cause the condition are vital for people to access the right support, plan for the future, and receive appropriate treatment. 

“Very early symptoms of dementia can be subtle and difficult to detect, but this study shows that problems with navigation could be some of the first changes in Alzheimer’s disease.”