Written by: Madison Estrella
Medically reviewed by: Rob Philibert MD PhD
The brain is one of our most vital organs as it controls our ability to breathe, eat, move, and to some extent, to live. Like all other organs, the brain is highly dependent on the wellbeing of the heart for it to function and as recent studies show, some brain disorders may be responsible for heart disease as well.
Dementia is one group of brain disorders linked to a higher risk for cardiovascular disease. In total, there are about 50 million people in the world who have dementia and nearly 10 million new cases each year. Dementia is the general term for brain disorders that involve the decline in memory and other vital brain functions. These brain disorders include Alzheimer’s Disease, Vascular Dementia, and Parkinson’s Disease. Unfortunately, dementia not only affects brain function, but it has also been linked to a higher risk for cardiovascular disease.
Don’t Forget About the Heart When Discussing Brain Health
As vital organs, the brain and heart are integral in the function of the other organs of the body, including one another. Thus, when we talk about brain disorders such as dementia, it only seems fit to consider how it affects the heart and vice versa.
The most apparent link between heart disease and dementia is their shared risk factors. Cardiovascular conditions, such as atherosclerosis (arterial blockage), inflammation, and hypertension (high blood pressure), can lead to decreased blood flow to the brain. [2] This can result in brain damage that leads to Vascular Dementia. Other risk factors for this form of dementia include obesity and Type 2 diabetes, which are also risk factors for heart disease. These cardiovascular-associated risk factors for dementia draw attention to the brain’s sensitivity to heart disease and cardiovascular disorders.
It is not much of a surprise that the development of dementia-based brain disorders can consequently worsen one’s cardiovascular health. This brain to heart pathway leading up to cardiovascular disease manifests in a number of different ways depending on which form of dementia an individual has.
Alzheimer’s Disease
Alzheimer’s is the most common form of dementia as it affects 1 in 9 people aged 65 or older. It is a progressive brain disease characterized by the loss of cognitive functions (dementia) and is believed to be caused by the abnormal buildup of amyloid protein plaques in the brain.
In a recent study conducted by the University of Genoa, Alzheimer’s patients were found to have left ventricular hypertrophy (or enlargement). [2] The left ventricle is considered the powerhouse of the heart as it is responsible for pumping an average of 70 mL of oxygenated blood throughout the body with each heartbeat. However, when the left ventricle’s walls become too thick (hypertrophy), it loses its elasticity and becomes less efficient at pumping blood. This can lead to a decrease in cardiac output and increased risk for heart failure.
Upon closer inspection, scientists found that the amyloid plaques that are implicated in Alzheimer’s Disease were also found in deposits in the heart. The build of amyloid plaques in the heart were believed to be responsible for the left ventricular hypertrophy observed in most Alzheimer’s patients.
Vascular Dementia
Vascular Dementia is the second most common form of dementia, following Alzeimer’s Disease. Unlike Alzheimer’s Disease, Vascular Dementia arises from brain damage caused by problems with the brain’s blood supply. It has a number of causes, but it is most commonly caused by stroke-induced damage. A stroke occurs when the blood supply to part of the brain is cut off. In the case of an ischemic stroke, the lack of a blood supply can be caused by a blood clot while a hemorrhagic stroke is caused by a leaky blood vessel.
Nonetheless, stroke, and thus Vascular Dementia, is a problem strongly associated with the cardiovascular system and cardiovascular disease. By nature of their relationship, the risk factors for cardiovascular disease, such as obesity, high cholesterol, and hypertension, can also increase an individual’s risk for Vascular Dementia if preventive action and lifestyle changes are not made.
Parkinson’s Disease
Dementia is also a common feature among people with Parkinson’s Disease. Parkinson’s Disease is a progressive nervous system disorder that affects movement. The disease gradually progresses from small symptoms, such as tremors and stiffness, to more noticeable ones, like speech slurring and the loss of autonomic functions (ie. blinking, swinging arms while walking, etc). These changes are largely attributed to the fact that Parkinson’s Disease arises from the impairment of the autonomic nervous system.
A population-based cohort study conducted by Korea University and Ansan Hospital in South Korea found that Parkinson’s Disease was associated with a higher risk for cardiovascular disease. When comparing the incidence of these cardiovascular conditions among individuals with and without Parkinson’s Disease, they found that Parkinson’s patients were 1.65 times more likely to experience congestive heart failure, 1.43 times more at risk for heart attack, and 1.42 times more likely to have an ischemic stroke. [4]
Although the mechanisms underlying the relationship between Parkinson’s Disease and heart disease are not fully understood, studies funded by the American Parkinson’s Disease Association are shedding light on the effect of autonomic dysfunction on cardiac disease in those with Parkinson’s Disease. In brief, neurons in the hypothalamus and brain stem are able to detect changes in the physiological and chemical state of the body. These neurons then relay this message to the autonomic nervous system, which will then send out a signal to the body to regulate its response. In a healthy person, the autonomic nervous system is capable of adequately controlling blood pressure through vasodilation and constriction, or by varying heart rate. However, in an individual that has Parkinson’s Disease, the brain’s ability to pass on autonomic messages to the heart may become impaired. In fact, some notable cardiac effects seen among Parkinson’s patients include variation in the intervals between heartbeats or a distinctive electrocardiogram. While these cardiac abnormalities can increase a Parkinson patient’s risk for heart disease, its progression to a serious heart condition and/or cardiac event can be prevented with the proper lifestyle changes.
What Needs to Change to Prevent Heart Disease?
Although dementia has been associated with heart disease, a diagnosis does not mean that the development of serious heart complications is definite. A lot of it can be prevented by adapting heart healthy lifestyle changes that encompasses a nutritious diet, exercise, and adequate rest. When caring for patients and loved ones with dementia, it is important to remember that their heart can and should be cared for, too.
Dementia and heart disease are both progressive illnesses, meaning that they can worsen with age. With that being said, those without dementia can prevent the progression of these diseases by taking on lifestyle changes. Whether it’s your brain health or heart health in question, you have the ability to reduce your risk by staying aware and being proactive about your own health.
References:
- World Health Organization. (n.d.). Dementia. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/dementia.
- Alzheimer’s Society. (n.d.). Risk Factors for Dementia. https://www.alzheimers.org.uk/sites/default/files/pdf/factsheet_risk_factors_for_dementia.pdf
- Tublin, J. M., Adelstein, J. M., del Monte, F., Combs, C. K., & Wold, L. E. (2019). Getting to the Heart of Alzheimer Disease. Circulation Research, 124(1), 142–149. https://doi.org/10.1161/circresaha.118.313563
- Schaich, C. L., Maurer, M. S., & Nadkarni, N. K. (2019). Amyloidosis of the Brain and Heart. JACC: Heart Failure, 7(2), 129–131. https://doi.org/10.1016/j.jchf.2018.12.014
- Park, J.-H., Kim, D.-H., Park, Y.-G., Kwon, D.-Y., Choi, M., Jung, J.-H., & Han, K. (2020). Association of Parkinson Disease With Risk of Cardiovascular Disease and All-Cause Mortality. Circulation, 141(14), 1205–1207. https://doi.org/10.1161/circulationaha.119.044948
- Cardiovascular Effects of Parkinson’s. American Parkinson Disease Association. (2019, August 19). https://www.apdaparkinson.org/article/heart-and-parkinsons/.