Going for a brisk daily walk or bike ride really can stave off Alzheimer's disease, according to new research.

It boosts white matter found deep within the brain that consists mainly of nerve fibres, or axons.

A study of older people found those with poor fitness levels had faster deterioration in the vital 'hubs' between neurons, putting them at greater risk of dementia.

Going for a brisk daily walk or bike ride really can stave off Alzheimer's disease, according to new research

'Improving people's fitness may improve their brain health'

Neurologist Assistant professor Kan Ding, of the University of Texas Southwestern, Dallas, said: 'This research supports the hypothesis that improving people's fitness may improve their brain health and slow down the ageing process.'

Nerve fibres are extensions of neurons surrounded by a pale 'sheath' called myelin. giving white matter its colour.

When they go awry the speed and transmission of electrical nerve signals slow down, leading to cognitive decline including the memory problems characteristic of Alzheimer's patients.

By comparison, grey matter is tissue found on the surface of the brain, known as the cortical region.

It contains the cell bodies of neurons, and has a darker hue.

White matter comprises millions of bundles of nerve fibres used by neurons to communicate across the brain.

White matter comprises millions of bundles of nerve fibres used by neurons to communicate across the brain

WHAT IS ALZHEIMER'S? Alzheimer's disease is a progressive, degenerative disease of the brain, in which build-up of abnormal proteins causes nerve cells to die. This disrupts the transmitters that carry messages, and causes the brain to shrink. More than 5 million people suffer from the disease in the US, where it is the 6th leading cause of death, and more than 1 million Britons have it. WHAT HAPPENS? As brain cells die, the functions they provide are lost. That includes memory, orientation and the ability to think and reason. The progress of the disease is slow and gradual. On average, patients live five to seven years after diagnosis, but some may live for ten to 15 years. EARLY SYMPTOMS: Loss of short-term memory

Disorientation

Behavioral changes

Mood swings

Difficulties dealing with money or making a phone call LATER SYMPTOMS: Severe memory loss, forgetting close family members, familiar objects or places

Becoming anxious and frustrated over inability to make sense of the world, leading to aggressive behavior

Eventually lose ability to walk

May have problems eating

The majority will eventually need 24-hour care Source: Alzheimer's Association Advertisement

Professor Ding and colleagues say their finding adds to evidence that exercise improves brain health and could be a lifesaver when it comes to preventing Alzheimer's.

The study published in the Journal of Alzheimer's Disease enrolled people at high risk of developing the condition who had early signs of memory loss, or mild cognitive impairment (MCI).

It found lower fitness levels were associated with weaker white matter, which in turn correlated with their brains working less efficiently.

Unlike previous studies that relied on study participants to assess their own fitness, the new research objectively measured cardiorespiratory fitness.

This was through a formula called maximal oxygen uptake which measures the most oxygen a person uses while exercising, giving an indication of how strong their lungs and heart are, and how fit they.

Scientists also used brain imaging to measure the functionality of each patient's white matter.

Participants were then given memory and other cognitive tests to measure brain function, establishing strong links between physical activity, mental health and cognition.

Professor Ding said it underlined the simple yet crucial mandate for human health - the importance of regular exercise.

The question is: why?

But the study also left plenty of unanswered questions about how fitness and Alzheimer's disease are intertwined.

Ding said these include what fitness level is needed to notably reduce the risk of dementia, and whether it is too late to intervene when patients begin showing symptoms.

Some of these topics are already being researched through a five-year national clinical trial led by his O'Donnell Brain Institute lab.

The trial, which includes six medical centres across the US, aims to determine whether regular aerobic exercise and taking specific medications to reduce high blood pressure and cholesterol levels can help preserve brain function.

The study also left plenty of unanswered questions

Scientists REVERSE Alzheimer's in middle-aged mice using the same drug as Merck A team at Cleveland Clinic published a paper showing they had successfully reversed Alzheimer's in a middle-aged lab mouse. Their trial used a BACE1 inhibitor, essentially the same method as Merck's, in a similar aged subject. They claim their tests on a 20-month-old mouse - equivalent to a 50-year-old human - show it could be possible to halt the disease if it is caught decades earlier than usual. Lead author Riqiang Yan admitted he was 'shocked' when their attempts to reduce amyloid plaque in mice completely eradicated the dangerous build-ups that slowly cripple the brain. Already aware of the Merck failure, Yan told Daily Mail Online last night that he still believes BACE1 is the answer to preventing and treating Alzheimer's. Yan envisions a future when these enzymes, known as BACE1 inhibitors, could be available as a vitamin that all humans take preventatively to stave off neurodegenerative disease. Advertisement

It involves more than 600 older adults at high risk to develop Alzheimer's.

Professor Rong Zhang, of UT Southwestern, who is overseeing the clinical trial, said: 'Evidence suggests what is bad for your heart is bad for your brain.

'We need studies like this to find out how the two are intertwined and hopefully find the right formula to help prevent Alzheimer's disease.'

He is director of the Cerebrovascular Laboratory in the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital, where the Dallas arm of the study is being carried out.

Fitness and forgetfulness

The research builds upon prior investigations linking healthy lifestyles to better brain function, including a 2013 study from Prof Zhang's team that found neuronal messages are more efficiently relayed in the brains of older adults who exercise.

In addition, other teams at the O'Donnell Brain Institute are designing tests for the early detection of patients who will develop dementia, and seeking methods to slow or stop the spread of toxic proteins associated with the disease such as beta-amyloid and tau, which are blamed for destroying certain groups of neurons in the brain.

Added Prof Ding: 'A lot of work remains to better understand and treat dementia. But, eventually, the hope is that our studies will convince people to exercise more.'

About 850,000 people in the UK have dementia, with Alzheimer's by far the most common form. The number of patients is set to rise to one million by 2025 and two million by 2050.

Identifying lifestyle factors that reduce the risk is vital, while scientists desperately hunt for a cure.