Blood flow, aging, and the brain
Blood flow in the brain changes as we age, a fact which may affect our risk of having a stroke.
Interrupt the flow of blood to any part of the brain, and the result can be a devastating stroke. Although the brain makes up only about 2% of the total body weight in humans, it receives 15% to 20% of the body's blood supply. Brain cells die if the supply of oxygen-carrying blood stops. Accordingly, the brain is exquisitely sensitive to changes in the levels of carbon dioxide and oxygen in the blood, and can quickly regulate blood flow to maintain oxygen delivery.
Heritage Senior Scholar Dr. Marc Poulin from the University of Calgary has a window on blood flow in the brain. He uses advanced Doppler ultrasound equipment-one of only two such set-ups in the world-to better understand diseases such as stroke. This powerful technology can analyze blood flow 100 times per second and average all the data within the time it takes for a single heartbeat.
Dr. Poulin's ultrasound studies cover many different areas, one of which is how blood flow in the brain changes with age in women and how this might affect their risk of stroke. Women are the faster-growing group of the senior population; since stroke rates in women double during each decade of life after the age of 55, the number of strokes in females will rise substantially over the next 15 years.
Blood supply and stroke
Dr. Poulin's current study looks at women aged 50 and older, and includes both physically fit and sedentary individuals. "We're looking to see how age affects the brain's ability to increase blood supply when challenged," explains Dr. Poulin. "We're hypothesizing that exercise boosts the brain's ability to do this. We're also doing cognitive-function tests on these women, and are hoping to relate cognitive function to cerebral blood flow. If these hypotheses show promise, we'll follow up with a larger study."
In addition to providing a better understanding of the mechanisms that control cerebral blood flow, this research has potential applications for stroke prevention. A stroke occurs when the blood supply to the brain stops; so the reduced ability to increase blood supply may make the brain particularly susceptible to stroke. One possible outcome of Dr. Poulin's research could be the development of a non-invasive test to identify susceptible individuals.
"I started off as a basic researcher, but over time I've become more and more interested in applying the knowledge from the lab to improve health care. Stroke is a very serious challenge. Circulatory diseases, including stroke, are the number one cause of major disability and death in adults in Canada; and the annual national cost of stroke is almost $3 billion. I'm hoping that my work will facilitate better assessment of stroke risk and potential interventions."