Population studies provides the opportunity to test newly developed biomarkers, exposures and genetic variation to study the relevance in association with phenotypes of interest or as predictors of progression from early-stage to established disease. It allows to understand the relative contribution of different factors including environmental, genetic factors and their interaction. The insights from epidemiological research should translate in maintain, enhance and promote people's health.

Epidemiological evidence and other information from, for example, health profiles, can be used to make informed decisions about their health. However, if the information about health risks is not communicated well it can create confusion or can be misinterpreted. Epidemiology has proved effective in establishing the major causes of diseases such as malaria but continues to experience difficulty in regard to more subtle health issues where causation is complex such as with immunization, hormone replacement therapy and alcohol consumption.

Dear  Samwel

Good question but difficult evidenced answer. Anyhow I will try to help and contribute a view which believe in.

Public health can be defined as"All organized public or private measures to prevent disease, promote health, and prolong life among the population. Its activities aim to:

1. Provide healthy conditions 

2. Focus on entire populations

3. Focus on the total system of health and health care

In all these public health need information which are partially provided through epidemiological methods, analysed by epidemiological methods and interepreted by epidemiological logic.

To elaborate further let us list some of the functions/ purposes/uses of epidemiology which can be simply seen as essential in achieving public health  functions (assessment, policy development and assurance of resources). The purposes of epidemiology are:

1.Description of pattern of disease:

Current pattern

Past time trends

Prediction of future trends

 2. Description of the natural history of disease

3. Identification of risk factors and protective factors

4.  Understanding the mechanism of disease transmission

 5. Classifying disease on the basis of:

Causes (aetiological) or   

Features (manifestation)

 6. Testing the effectiveness of interventions

7.Clinical decision analysis-clinical epidemiology.

 8.Administrative uses- planning, organization and evaluation of health care services.

9. Identifying population health needs

Epidemioogy is working within public health framework. You may have a look at 10 Essential public health operations http://www.euro.who.int/en/health-topics/Health-systems/public-health-services/policy/the-10-essential-public-health-operations

I think epidemiology as an essential tool, coming alongside both basic and applied medical and social research, to guide public institutions and society towards rational options for useful and sustainable health policies, affording them the possibility to control if their actions were successful or not in term of real health results.

Epidemiology moves along different paths (which efficacy rise if they are connected inside a web and if they are strongly supported by independent resources, remaining free from conflicting interests), i.e. population and hospital based registries, cohort and case-control studies, alert systems based upon a systemic and prompt recording of sentinel events, and so on.

The web of epidemiology needs to be connected with systems dedicated to the study of environmental and social risk factors, permitting to comprehend causative relations.

Epidemiology (such as the studies about risk factors) is absolutely not a luxury article.

Population studies provides the opportunity to test newly developed biomarkers, exposures and genetic variation to study the relevance in association with phenotypes of interest or as predictors of progression from early-stage to established disease. It allows to understand the relative contribution of different factors including environmental, genetic factors and their interaction. The insights from epidemiological research should translate in maintain, enhance and promote people's health.

Great contribution, Tim ! It opens a wide range of opportunities to glance at several practical consequences of the multistage carcinogenesis model, beginning from the study of the combined effects of reiterated exposures to mutagens and any carcinogens, both in more and less susceptible subjects, and of stopping such exposures during the latency period.