Exploring the link between brain health and heart health.
Although our brains are small in comparison to the rest of our bodies, they use over 20% of our total oxygen. As oxygen is transported into and around the brain by the circulatory system of blood vessels, the health of these blood vessels and the heart is crucial for ensuring enough oxygen gets to the brain.
Another name for the blood vessels in the body is the vascular system. Vascular dementia is the second most common type of dementia for people aged over 65. It is caused by brain damage due to lack of blood flow to the brain.
Reduced blood flow means less oxygen can get to the brain. All cells in the body need oxygen to survive, so brain cells that are starved of oxygen will eventually die. This can happen slowly over time or quickly as a result of complete blockage of a blood vessel, leading to a stroke.
How the damage occurs dictates the subtype of vascular dementia, which include stroke-related dementia, single-infarct and multi-infarct dementia, and subcortical dementia. You can read more about the different types of vascular dementia in this factsheet from Alzheimer’s Society.
The heart is responsible for pumping blood through the vascular system, and together with the blood vessels makes up the cardiovascular system. Therefore, any problems with the heart directly affect blood flow.
Cardiovascular disease (CVD)
Cardiovascular disease is the medical term for conditions that affect the heart and blood vessels, such as heart attacks and stroke. CVD is caused by the combination of several factors including high blood pressure, obesity, diabetes, and high cholesterol.
High blood pressure (known medically as hypertension) strains the cardiovascular system. This increases the risk of stroke, heart attacks, and abnormal bleeding from tiny blood vessels in the brain, among a range of other diseases. For these reasons, high blood pressure is associated with cognitive decline and dementia.
A high level of the fatty substance cholesterol in the blood is linked to an increased risk of dementia. Cholesterol builds up on the inside of arteries, making it more difficult for blood to flow through them. This can eventually completely block arteries leading to heart attacks, stroke and vascular dementia. There is also research suggesting a disruption in the breakdown of cholesterol could be why high levels of cholesterol may accelerate dementia progression.
Diabetes is a condition characterised by high levels of sugar in the blood. Diabetes can dramatically increase a person’s risk of both vascular dementia and Alzheimer’s disease. This is because high blood sugar causes inflammation which damages both blood vessels and brain cells.
Insulin is an important hormone that helps your body use sugar to make energy. Research is now emerging that insulin also has several crucial roles in the brain. People with diabetes often don’t have enough insulin available, which can cause problems for blood vessels and the brain.
Obesity increases your chances of having diabetes and high blood pressure, which are both risk factors for cardiovascular disease. It has also been shown that people who are obese are more likely to develop dementia.
What you can do
Thankfully, lots of the factors that cause CVD are preventable, so lifestyle changes can reduce your risk of both CVD and dementia.
Type 1 diabetes is caused by genes, so is sadly not preventable, but a major cause of type 2 diabetes is a diet high in sugary foods. Cutting down on the amount of sugar you consume is the most effective way to prevent diabetes, which will in turn help to prevent CVD and dementia.
Smoking is another cause of type 2 diabetes and also directly damages blood vessels and increases the chances of blood clots. So, not smoking will tackle multiple risk factors for CVD and help prevent dementia.
As well as too much sugar, diets that are high in junk food increase a person’s risk of CVD. Too much salt, caffeine and alcohol can raise blood pressure to dangerous levels, while fatty foods result in high levels of cholesterol in the blood.
‘Good cholesterol’ – found in foods like olive oil, beans and nuts – can reduce the amount of dangerous cholesterol in the blood. Read our blog post for more detail on how diet affects dementia.
A range of unhealthy foods lead to obesity but losing weight can significantly reduce the risk of CVD and dementia. Exercising helps to prevent obesity and lower cholesterol levels and blood pressure. It is recommended for adults to exercise for at least 150 minutes – that’s two and a half hours – each week.
Cardiovascular health may be even more important in mid-life than later life to prevent dementia. This means the crucial time to implement these preventative health behaviours is when you are middle-aged – before dementia has begun to develop.
What to read next
21 October 2020
Stroke and vascular dementia are intrinsically related, with both being a risk factor for the other. Researchers at the University of Edinburgh led by Professor Joanna Wardlaw are studying stroke patients to learn more about the cognitive impairment that often follows a stroke, thanks to a grant from DPUK that allowed them to get started.