It has been known for many years that people with untreated high
blood pressures have a greater than normal risk of developing strokes, heart
and kidney disease, with a consequent reduction in life expectancy. This was
first observed by life assurance companies from follow-up studies of people
who had their blood pressure measured during medical examinations for
insurance purposes. It was found that the higher the blood pressure the
shorter was the life expectancy, if anything, the insurance statistics
underestimate the importance of blood pressure since they take no account
of the disability which often occurs when patients survive an illness such as
stroke. It is worth remembering that high blood pressure is the most
important known cause of strokes. Someone of 40, for instance, is 30 times
as likely to have a stroke if his blood pressure is high compared with
someone with a normal blood pressure. It should also be emphasised that
strokes and heart attacks caused by hypertension often occur in individuals
who have no symptoms up to the time of the illness.