The current guidelines set by the NHS and endorsed by the various specialist groups working with heart and vascular disease recommend that for people not in the above groups (ie those with no known vascular disease) that a risk of developing heart attack or stroke within the next ten years is calculated.
That risk is based on the person's:-
If the calculated risk is less than 15% of developing a heart attack or stroke then usually a statin will not be prescribed
If the risk is greater than 20% then a statin is recommended.
Between 15% and 20% whether to prescribe a statin may be based on further less easily quantifiable risk factors such as whether or not there is a strong history of heart disease in close family members at a young age.
This is called primary prevention - trying to prevent new disease developing in people already recognised to be at higher risk than the population generally. If you do not have cardiovascular disease and you know your blood pressure, total cholesterol and HDL cholesterol you can calculate your ten year risk by following the link below. This will take you to an external site run by the University of Edinburgh. You will find several different ways of calculating the risk which are based on different population studies. There are calculations based on an American population (CDV Frammingham), a Scottish population (CDV ASSIGN) and based on the risk caclulations used by the Joint Britsh Societies and published in the British National Formulary (CDV BNF). In the results, CDV risk is that of developing coronary heart disease, (dying of cardiovascular disease, having a heart attack or developing new angina), MI risk is the risk of having a heart attack (myocardial infarction) and stroke risk is the risk of having a stroke or mini-stroke (TIA).
It should be noted that the figures used should be those for blood pressure and cholesterol before any treatment has been given. I would recommend using the CDV (BNF) calculator.
I am frequently asked the same questions about cholesterol and statins and some of these can be seen by following the link below.