in addition primary prevention activities such as tobacco control programmes have also had a real impact on cvd mortality a number of countries have used the socalled impact model to explain the changes in coronary heart disease chd mortality rates observed in a population this model developed by academics at the university of liverpool uses longitudinal data on major population risk factors smoking high systolic blood pressure elevated total blood cholesterol obesity diabetes and physical inactivity and from medical and surgical treatments to quantify the contribution that treatments and risk factor reductions has made to the decline in chd mortality capewell et al