Healthy brain, healthy heart: unlocking multiorgan connection

June 26, 2023

There are an estimated 620 million people worldwide living with heart and circulatory diseases, with approximately 60 million people developing a heart or circulatory disease each year: The most common cardiovascular conditions are coronary (ischemic) heart disease (global prevalence estimated at 200 million in 2019), peripheral arterial (vascular) disease (110 million), stroke (100 million), and atrial fibrillation (60 million). According to statistics given by the British Heart Foundation in its newly published Global Heart & Circulatory Diseases Factsheet, this number is set to rise due to changing lifestyles, an aging and expanding population, and higher survival rates from heart attacks and strokes.

Aside from changing lifestyles and risk factors that predispose a person to heart disease, a new study investigated the link between brain health and heart health.

Why brain health is essential for physical well-being

Because the brain is the command center of the body, it is critical for general physical health. It regulates and coordinates nearly every bodily function and process, including crucial activities like breathing, heart rate, digestion, as well as sleep.

Memory, focus, problem-solving, and decision-making are all supported by a healthy brain. These cognitive skills are critical for daily activities, work productivity, and overall well-being.

The brain has an important role in controlling both intentional and involuntary movements. It is in charge of coordinating muscle motions, balance, coordination, and reflexes. A healthy brain promotes physical activities and reduces the risk of accidents and injuries by ensuring smooth and effective motor abilities.

The brain regulates the release of hormones from many glands, including the pituitary gland, also known as the “master gland.” Hormones regulate a variety of biological activities, including growth, metabolism, reproduction, and stress response. A skewed or diseased brain can cause hormonal imbalances and associated health problems.

A healthy brain promotes good immune system function, which improves the body’s ability to fight infections, illnesses, and inflammation. It is also in responsible for emotion regulation and mental well-being. Emotional stability, resilience, and the ability to cope with stress are all aided by good brain health. Poor brain health, on the other hand, can lead to mood disorders, anxiety, depression, and other mental health issues, all of which can have a severe impact on physical health.

A balanced diet, frequent physical activity, mental stimulation, social interaction, stress management, and quality sleep can all help to improve brain health.

Heart and mind connection – a study

Stroke, dementia, cerebral small vessel disease, and cognitive impairment are all caused by cardiovascular illnesses. For example, studies have revealed that atrial fibrillation, even in those who have never had a stroke, is connected with an elevated risk of dementia and silent cerebral damage.

Heart failure has been related to cognitive impairment and dementia due to decreased cerebral blood supply induced by a failing heart. In contrast, mental problems and unfavorable psychological factors may contribute to the initial development and progression of cardiovascular disease. Individuals suffering from disorders such as schizophrenia, bipolar disorder, epilepsy, or depression are predisposed to cardiovascular disease.

Despite this developing understanding, past studies on heart-brain connections and associated risk factors were narrow in scope, focused on specific disorders or employing tiny sample sizes. As a result, our total understanding of the anatomical and functional relationships between the heart and brain is still limited.

In a recent study scientists from UNC-Chapel Hill, the University of Pennsylvania, and Purdue University, who made use of large amounts of magnetic resonance imaging (MRI) data, found that there is mounting evidence of a close connection between heart health and brain health, with cardiovascular diseases potentially contributing to brain diseases like stroke, dementia, and cognitive impairment.

MRI is a valuable technique for assessing both the heart and the brain, as well as for developing biomarkers and endophenotypes for various clinical outcomes.

Although recent large-scale assessments of heart and brain MRI-derived features have been conducted separately, the researchers claimed that few studies have looked into the potential for multiorgan MRI to evaluate heart-brain links and find shared genetic factors.

The work, led by the Biostatistics and Imaging Genomics Analysis Lab’s Statistics and Signal group (BIG-S2) at UNC, was published in the journal Science. Bingxin Zhao, PhD, assistant professor of statistics and data science at the University of Pennsylvania and doctorate alumnus of the UNC Gillings School of Global Public Health, is the study’s first author. Yue Yang, Zirui Fan, Zhengyi Wu, Xifeng Wang, Tianyou Luo, Jiarui Tang, Di Xiong, Jie Chen, Yue Shan, Chalmer Tomlinson, and Ziliang Zhu are also authors, as are Professors Yun Li, Jason L. Stein, and Hongtu Zhu.

The researchers used data from nearly 40,000 subjects in the UK Biobank study to perform their investigation, which included expertise in biostatistics, statistics, data science, radiography, computer science, and genetics. They used a sophisticated pipeline to extract 82 cardiac MRI attributes, including chamber, aortic segment, and regional characteristics. They discovered a wide range of brain MRI features at the same time, including structural, diffusion, and functional measures, offering a comprehensive picture of brain abnormalities and connectivity.

The findings, which controlled for a variety of parameters, indicated that heart MRI features had a significant influence on brain health across many imaging modalities. In particular, abnormalities in the left ventricle were substantially linked to poorer white matter architecture in the brain.

The researchers effectively revealed the genetic architecture underlying heart-brain interactions using genome-wide association studies (GWAS). In total, 80 genetic loci were shown to be linked to heart MRI characteristics. Both sexes had the same genetic impacts on heart structure and function.

The study also discovered similar genetic impacts and colocalizations between heart and brain disorders as well as complicated features. For example, abnormal cardiac wall thickness has been associated to an increased risk of stroke. The researchers also used Mendelian randomization

to look for causal genetic relationships, and they discovered that negative cardiac characteristics may have hereditary consequences on psychiatric diseases and depression.

According to the researchers, this work has major implications for illness risk prediction and prevention through expanding awareness of the complicated interactions between the heart and brain. This study’s multiorgan perspective opens up new avenues for mitigating the detrimental impact of organ illnesses on one another and improving overall human health.

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