SYDNEY: Heart disease may affect more than your heart – it could also kill off your brain cells, say Australian researchers.
Heart failure and disease caused by reduced blood supply to the heart can lead to a loss of brain cells and reduced cognitive abilities. This finding, published by a team of scientists in a recent issue of the European Heart Journal, suggests that heart disease may affect a part of our brains that governs mentally demanding tasks.
Uncovering this connection may help scientists to develop more efficient treatment strategies for heart disease and might even aid our understanding of cognitive decline and dementia.
A heart less efficient in pumping blood causes other organs to suffer, said lead author Osvaldo Almeida from the Centre for Medical Research at the University of Western Australia in Perth. But the link between heart disease and damage to the brain involves a number of factors besides reduced blood flow, and Almeida’s team set out to pinpoint exactly what these are.
Heart disease and memory
When ischaemic heart disease (IHD) – also called coronary heart disease – occurs, the coronary arteries taking blood to the heart are totally or partly blocked. This often leads to a heart attack and then heart failure.
Researchers have long known of a correlation between heart failure and reduced cognitive abilities, but it’s been difficult to separate the effects of heart failure from those of IHD, which is often the underlying cause of heart failure. “When people have heart failure and the heart is not pumping properly, the brain [may] suffer because of lack of oxygen or glucose,” said Almeida.
But this study found a significant loss of brain cells in people suffering from IHD, even when their heart was pumping normally. And even in patients affected by heart failure, the loss of brain cells wasn’t very strongly associated with cardiac output, which is the amount of blood the heart is able to pump, Almeida added.
Testing the brain
Almeida’s team used magnetic resonance imaging (MRI) of the brain to investigate grey matter volume of about 150 people: a control group, patients suffering from IHD (but with fully functional hearts) and patients suffering from IHD and heart failure. Next, they assessed the groups’ cognitive abilities using well-established neuropsychological tests.
“What we found is that there is a graded loss of brain cells from controls to heart failure [patients]. So the people who had IHD, too, lost brain cells compared to controls, but to a much lesser extent than those people with heart failure,” said Almeida. These results further support the idea that heart failure and reduced pumping power of the heart is not solely responsible for the observed changes in the brain.
Pinpointing the problem
People with heart failure lost more brain cells than those with IHD (but efficiently pumping hearts) when compared to the control group. The research also showed impairments to memory and psychomotor speed, among other cognitive abilities, in those patients with heart failure compared to the healthy people.
“There are a range of things that happen in heart failure that have the potential to affect brain function. You get changes in a whole range of hormonal systems and the autonomic [nervous] system,” said Leonard Arnolda, co-author of the study and a cardiologist at the Australian National University Medical School in Canberra. The exact effect that these physiological and biochemical changes have on the brain of heart failure patients is what the team is trying to work out now.
Heart disease and loss of cognitive ability have many risk factors in common: “Inactivity, smoking, hypertension, diabetes and [elevated blood cholesterol levels],” said Almeida. “People need to be mindful that lifestyle choices and practices will have implications not only for their heart but also for their brain health.”
Treatment for cognitive decline
“Clinically and based on research we know that people with heart failure do have memory problems. Their thinking slows down,” commented Craig Anderson, director of the Neurological and Mental Health Division of the George Institute for Global Health at the University of Sydney. “What this study adds is where in the brain there are problems.”
Andrew Sindone, director of the Heart Failure Unit at the Concord Hospital in Sydney, who was not involved in the study, agreed. “We’ve known for a long time there’s something going on but now this [study has] started to pinpoint where it is.”
Almeida added that this work could eventually help our understanding of cognitive decline as people get older. “If we’re able to identify the physiological mechanisms that are involved, that might also be beneficial for people who don’t have heart failure.”