Most of the potential gain in health of human populations results from primary preventive medicine which includes public health methods such as sanitation and vaccination. Secondary preventive medicine commences after symptoms of a health problem present in an individual and often includes life style adjustment but increasingly medications that modify risk factors for disease.
Risk stratification for a population can be very useful but it must be remembered that usually the most effective way to alleviate the overall burden of illness in a population is to ensure appropriate resource effective interventions are directed at low and medium risk members of the population as well as those at high risk. So costly preventive therapies directed at those at high risk may actually be less effective with some illnesses than low cost life style interventions in those at low risk.
Preventive medicine or disease prevention?
Various related terms have been used over the years - health promotion, disease- or ill-health-prevention being another two. Preventive medicine would imply what doctors, or more broadly, the "health" services (which are, after all, mainly disease services) can do to to prevent disease and to promote good health.
Ethical aspects of preventive medicine
When a patient requests treatment, they may be content for a doctor to do whatever they think might help, and to accept poorly evidenced treatment, if the pay-off is an improvement in their (percieved to be poor) health.
By contrast, preventive medicine usually approaches people who are or believe themselves to be healthy, and risks turning them into patients (diagnosing susceptibility to future disease). As there are harms potentially associated with this, the onus on the doctor to be certain that what they are doing is likely to be beneficial is much higher: so the evidence-base for interventions - such as screening - must be excellent.