There are two types of stroke - those caused by blood clots in the brain and those that occur when blood vessels burst. In both cases, the brain is starved of oxygen, damaging or killing cells.
Four out of five people who die from coronary heart disease are aged 65 or older. The risk of stroke doubles with each decade after the age of 55. Men are more at risk than women and have attacks earlier in life. But death rates from heart disease and stroke for women are twice as high as those for all forms of cancer. The risk for women increases as they approach menopause and continues to rise a they get older, possibly because of the loss of the natural hormone oestrogen.
Sufferers are often left with difficulty talking, walking and performing other basic tasks. The chance of suffering a stroke is cut by eating healthily, quitting smoking and drinking less alcohol. People at risk of stroke are often treated with aspirin.
After a stroke, various drug treatments are available and rehabilitation is commonly used to improve patients' speech and movement.
The higher the blood cholesterol level, the higher the risk of coronary heart disease, particularly if it is combined with any of the other risk factors. Diet is one cause of high cholesterol - others are age, sex and family history.
High levels of LDL (low-density lipoprotein), or "bad cholesterol", are dangerous, while high levels of HDL (high-density lipoprotein), or "good cholesterol" lower the risk of heart disease and stroke. Aspirin is effective in preventing clotting of the blood, by reducing the "stickiness" of the platelets.
A smaller dose is needed than is required to relieve a headache.