Millions of Brits living with heart disease, some undiagnosed, could be at increased risk of dementia a team of experts has warned. 

Yet, four in ten cases of the memory robbing disorder could be prevented with simple lifestyle changes, according to recent research. 

Experts said several heart conditions, ranging from the an irregular heart beat to the aftermath of a heart attack dramatically increases the risk of cognitive decline later in life.

And while an near 8million Brits are already living with such conditions, some 300,000 are thought to be undiagnosed but still at risk. 

Three common cardiovascular diseases in adults — heart failure, atrial fibrillation and coronary heart disease — are linked to cognitive impairment and increased risk of dementia, a scientific statement from the American Heart Association (AHA) published in the journal, Stroke, revealed. 

Cognitive impairment is considered a precursor to dementia a disorder that robs sufferers of their memory and independence. 

People with atrial fibrillation, a condition that causes an irregular and abnormally fast heart rate, had the largest risk of developing cognitive problems at 39 per cent, followed by those with heart disease who had an a 27 per cent higher chance of developing dementia.  

Additionally, the AHA warned about half of heart attack and heart failure victims also develop cognitive decline after the emergency. 

There are around 7.6million people living with a heart or circulatory disease in the UK and 121.5million in the US. 

More than 1.5million people in the UK have been diagnosed with atrial fibrillation in the UK and it is thought to affect up to 6million Americans a year, while heart failure affects over one million Brits and nearly 6.5 million Americans. 

Professor Fernando Testai, an expert of neurology and rehabilitation at the University of Illinois, and chair of the experts that co-wrote the statement said cognitive decline in people had a dramatic impact at both an individual and societal level.  

'Managing heart health from an early age is important to prevent cardiovascular disease and cardiac events, protect brain health and reduce the risk of cognitive decline in later life,' he said.

A meta-analysis of previous studies found that almost 50 per cent of people with heart failure experience some kind of cognitive impairment that may impact language, memory or executive function. 

There are several links between heart failure and brain injury; reduced blood flow can cause mini-strokes or silent brain injuries, plus chronic inflammation may also contribute to brain damage.

Atrial fibrillation (AF), a condition marked by an irregular and abnormally fast heart rate, also increases the risk of dementia. 

Dubbed a 'silent killer', it is caused by random electrical impulses incorrectly firing from the top chambers of the heart which override the heart’s regular rhythm. 

This can lead to symptoms such as palpitations and breathlessness and in some cases, heart failure. 

Both dementia and AF share several risk factors including high blood pressure, Type 2 diabetes, heart failure, smoking, vascular disease and sleep-disordered breathing.

Strokes and small brain bleeds are also more common in people with AF and linked to cognitive decline.

It's thought like heart failure, reduced cardiac output with AF may compromise blood flow to key areas of the brain responsible for cognitive function.

Inflammation is associated with both AF and Alzheimer's disease and inflammatory biomarkers are associated with increased risk of blood clots and brain injury, experts say. 

More than 1.5million people in the UK have been diagnosed with AF, about one in 50 people.

But an estimated additional 270,000 people are thought to have AF but remain undiagnosed and unaware of the danger, according to British Heart Foundation.

Doctors remain baffled as to the exact cause of atrial fibrillation, which can lead to strokes. 

It is, however, known to be more common in people with high blood pressure — a consequence of being obese. 

The AHA authors stress that effective treatment of AF may reduce cognitive decline. 

Coronary heart disease also significantly increases the risk of dementia and cognitive impairment.

Data from multiple, large-scale studies show a heart attack is linked to a steeper decline in memory and executive function. 

Elevated levels of calcium buildup in the arteries are also linked to a greater risk of developing dementia. 

High blood pressure and type 2 diabetes, which are both risk factors for heart disease, cause inflammation that affects the blood-brain barrier and reduces blood flow to the brain, leading to cognitive decline and dementia.   

Heart disease is also linked to reduced brain blood flow, resulting in cognitive impairment. 

The same issues with reduced blood flow in the brain are also seen in patients with Alzheimer's, suggesting a close link between blood vessel damage and brain degeneration.

The AHA authors added that genetic factors that increase heart disease risk may also contribute to brain shrinkage and cognitive decline.

Medication such as blood pressure treatment could help to reduce mild cognitive impairment, but study authors say it hasn't been shown to help prevent dementia. 

Other studies looking at heart health and cognitive decline also suggest heart health can be managed with lifestyle interventions such as diet and exercise, which can also prevent cognitive decline. 

Professor Testai said: 'Although new medications with the potential to treat Alzheimer's disease are being developed, the medical community is well aware that prevention is better than a cure. 

'More research is needed to confirm and outline how cardiovascular care can improve brain health. In addition, more research is needed to understand the ways gender, race and ethnicity may influence the connection between the brain and the heart.'