Three types of prevention are advocated by WHO: primordial, primary and secondary. Prevention may be population-based or target high-risk groups. In some types of heart disease (e.g. RHD), secondary prevention is the most practical. In the case of CAD and hypertension, scientists now recommend primordial prevention (prevention of appearance of risk factors) as primary prevention, i.e. control of risk factors has been done in many interventional studies in Europe and the USA with only partial response.