Stroke is the third most common cause of mortality and is age dependent. The risk under 15 years of age is 1 in 100,000, rising to 100 per 100,000 between the ages of 45 and 54, and increasing to over 1 in 33 for those over 85 years of age. There is some variation in age-adjusted annual incidence rates in different countries of the world. Race, sex, social background and ethnic origin affect the incidence. Caucasians have a lower incidence than non-Caucasians and it is higher in blacks than in whites in the USA. There are also differences within the same race living in different parts of the world - it is three times higher in males living in Japan than those living in Hawaii.
Cerebral infarction (embolic or thrombotic) accounts for over 70% of strokes, cerebral haemorrhage for about 20% and subarachnoid haemorrhage for the remainder.
Mortality from strokes has been decreasing in most western nations for many decades although there is considerable variation between different countries. The most striking decrease has occurred in Japan. Most of the decrease is due to reduced incidence but some is due to better management. The decrease affects both men and women although the incidence for men is up to 50% higher. A greater part of the reducing incidence is due to a decline in intracerebral haemorrhage and cerebral infarction; the incidence of subarachnoid haemorrhage has remained fairly constant.
Atherosclerosis is by far the most common vasculopathy causing cerebral infarction and cerebral infarction is approximately 10 times more common than cerebral haemorrhage in the United States of America. There is considerable variation in the incidence of infarction and haemorrhage in different parts of the world; in the Orient, for example, haemorrhage is almost as common as infarction.