Elderly people with hardened arteries are more likely to have brains that bear early signs of Alzheimer's, a study has found.
The research points to a strong link between heart and artery health and the risk of developing dementia.
Stiffness and narrowing of the arteries is caused by the build up of hard scaly material on blood vessel walls.
The study found that even in people who appeared healthy, artery hardening was associated with brain deposits of beta-amyloid protein, a hallmark of Alzheimer's disease.
Scientists studied 91 people with an average age of 87 who had no symptoms of dementia. Scans were taken of their brains and arterial stiffnesss measured by comparing blood pressure in the ankle and arm.
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Signs Of Dementia
For every unit increase in arterial stiffness, patients were twice as likely to have beta-amyloid brain plaques.
People with beta-amyloid deposits were also more likely to be suffering from high blood pressure.
Arterial stiffness was highest in those participants who had both amyloid plaques and white matter brain lesions, regions of neurological damage.
"These two conditions may be a 'double-hit' that contributes to the development of dementia," said lead researcher Dr Timothy Hughes, from the University of Pittsburgh in the US. "Compared to people who had low amounts of amyloid plaques and brain lesions, each unit of increase in arterial stiffness was associated with a two to four-fold increase in the odds of having both amyloid plaques and a high amount of brain lesions.
"This is more evidence that cardiovascular health leads to a healthy brain."
The scientists, whose research is published in the latest online issue of the journal Neurology, based their findings on the Ankle Brachial Index (ABI) - a measurement of the ratio of blood pressure in the lower legs and the arms.
They found that people with hardened arteries were more likely to have beta-amyloid plaques even in the absence of high blood pressure.
Dr Doug Brown, director of research and development at the Alzheimer's Society, said: "This research suggests that hardening of the blood vessels could contribute to dementia in more than one way, providing further evidence that what's good for your heart is good for your brain. You can be kind to these vital organs and reduce your risk of developing dementia by taking part in regular exercise, eating a balanced diet and avoiding smoking.
"People over 40 should also get their blood pressure checked regularly. This study reaffirms this guidance, suggesting a link between high blood pressure and beta-amyloid plaques in the brain, which are a hallmark of Alzheimer's disease.
'It's important to note that this research was conducted in older people without dementia, so we don't know if the increase in amyloid plaques in those with hardened arteries would be enough to cause the condition. Understanding the progression of Alzheimer's before symptoms become apparent is vital in helping us unravel the underlying causes of dementia and ultimately finding a cure."
Dr Simon Ridley, from the charity Alzheimer's Research UK, said: "This study reports an association between some indicators of poor cardiovascular health and higher amounts of amyloid in the brain, but we don't know from this research whether these people would have been more likely to go on to develop Alzheimer's.
"It is clear that some people can have amyloid in their brains but never go on to develop symptoms of the disease and it is important that funds are invested in research to understand more about why this is.
"We do know from previous research that what is good for your heart appears to be good for your head. Evidence suggests that regular exercise, a balanced diet, healthy weight, not smoking and keeping blood pressure and cholesterol in check could be ways to keep our brains healthy as we get older."