1. What is stroke?
Optimal function of the human brain is critically dependent on the consistency of the blood flow circulating the brain. Through a complex network of capillary vessels, the brain receives the necessary oxygen and nutrients and leaves its metabolic waste. Any obstruction or impairment to this vascular route will lead to oxygen deprivation of the brain, initiating a cascade of mechanism that ultimately results in brain tissue ischemia and cell death.
There are two types of stroke: ischemic and hemorrhagic. Hemorrhagic stroke, more common is some region, especially Asia, is caused by internal bleeding of the brain. This could be caused by trauma leading to rupture of the blood vessel or an aneurysm (weakening of the artery wall, causing blood to flow into the brain). Blood flood into the surrounding space, resulting in increased compression to the brain tissues. The outcome is fatal and almost 50% of patients will die.
Ischemic stroke is the more common type of stroke, identified in 80% of the incidences. It is caused by the obstruction or impairment of blood flow in the artery, causing oxygen deprivation of certain parts of the brain. Obstruction can be caused by fatty plaque deposited on the artery wall, a condition called atherosclerosis, or by a clot that disrupt the flow of blood. A clot can either be a thrombus, in which blood aggregation causes the blockage, or an embolus, in which the blood clot is created elsewhere and travels to the blockage site. Within seconds of lacking oxygen, brain cells start to die and brain damage occurs.
Stroke is the leading cause of disability and third leading cause of death worldwide. On average, strokes in the USA strike once every 40 seconds and cause death every 4 minutes, with an estimated 41.6% death rate in 2007. With an aging population, the absolute numbers are likely to rise. Among survivors, work capacity is compromised in 70% of victims, and 30% need assistance with self-care. Hence, the disease burden is great. The estimated cost for stroke is 73.7 billion dollars in 2010 (USA) and projected to be 1.52 trillion dollars in 2050 (in 2005 dollars).
3. Risk factors
– Lifestyle factors: obesity, physical inactivity, heavy drinking and drug abuse.
– Medical conditions: high blood pressure, high cholesterol, diabetes and a history of cardiovascular diseases.
– Other genetic factors are also related to an increase in CVA risk: age, race and gender.