Stroke and Alzheimer’s disease are both much too common, debilitating brain disorders. According to the Centers for Disease Control and Prevention (CDC), stroke is the fourth leading cause of death in the United States, and Alzheimer’s disease is the most common form of dementia. UCLA researchers have developed a new, noninvasive method to measure artery stiffness in the brain. The research may lead to methods to prevent stroke and the early diagnoses of Alzheimer’s disease. They published their findings this week in the peer-reviewed journal NeuroImage.
The researchers used a new MRI technique that measured the volume of cerebral arteries twice using a technique called Arterial Spin Labeling; the procedure can magnetically “label” the blood in arteries without the use of an external agent. The investigators measured once at systole of the cardiac cycle, when the heart was pumping the blood into the brain, and again at diastole, when the heart was relaxing. They found that the stiffer the arteries were, the smaller the change in the arterial blood volume between the two cardiac phases; this was because stiff arteries are not as able to change shape or comply with the blood pressure changes as well as elastic arteries can, explained senior author Danny J.J. Wang, PhD, an associate professor of neurology and a researcher in the Ahmanson-Lovelace Brain Mapping Center at UCLA.
Dr. Wang said, “Vascular compliance is a useful marker for a number of cardiovascular diseases, such as hypertension and diabetes. Growing evidence suggests intracranial vascular pathology also may be associated with the origin and progression of cerebrovascular disorders and neurodegenerative diseases, such as Alzheimer’s disease, which is the sixth leading cause of death in the United States. However, to date, few methods are available to assess it.”
The investigators compared stiffness measurements in young and elderly patients; they found that arterial stiffness is significantly increased in elderly patients. This finding is consistent with the theory that aging is associated with stiffening of the arteries. In addition, they found that increased arterial stiffness is associated with reduced cerebral blood flow; this suggested that stiff arteries restrict the blood supply to the brain. They also found that artery stiffness correlated with the stiffness of the largest artery of the human body, the aorta.
“We hope our technique can provide an early marker for a number of socioeconomically important diseases like Alzheimer’s,” explained first author Lirong Yan, an assistant researcher in the UCLA Department of Neurology. He added, “A number of studies suggest that vascular dysfunctions, including arterial stiffening, are associated with the development of Alzheimer’s. The development of early bio- or imaging markers for Alzheimer’s is of great importance for slowing disease progression. Hardened arteries due to the accumulation of plaques on the vessel walls also is linked to cerebrovascular disorders such as stroke. We hope our technique may provide an early marker for the prevention of stroke.”
The study authors note that the need for a new approach to treat of Alzheimer’s disease is urgent. The number of cases in the United States is expected to increase from the current number of about five to six million to 15 million by 2050. The costs to family life and on the healthcare system are enormous. Alzheimer’s and other dementias are projected to cost the United States $226 billion in 2015 alone, with that number rising to as high as $1.1 trillion in 2050.