3. to what extent does epidemiology rely on medical disciplines for its content, and to what extent does it draw upon other disciplines? explain the statement that epidemiology is interdisciplinary.

Explanation:Epidemiology is a core component of public health school curricula, reflecting its pivotal role in the health sciences. Recently, integration of pathology into epidemiologic studies has become increasingly common, because many diseases are being defined by molecular pathogenic mechanisms. As current disease classification schemes become more reflective of pathobiology, epidemiologists must appreciate the rationale behind disease classifications and subtyping in their study designs.  

Excellence in research and education requires the combined efforts of many different disciplines. As fundamental disciplines of biomedical and public health sciences, both pathology and epidemiology are fields of study of the entire spectrum of human diseases—the former focused on disease mechanisms in individual cases, the latter on patterns of disease in populations. The importance of these fields is well exemplified by the universal presence of pathology in medical school curricula and that of epidemiology in public health school curricula. Because of advances in both laboratory technologies and epidemiologic methods, pathology and epidemiology have become compartmentalized in schools of medicine and public health, respectively. By virtue of the training in both pathology and epidemiology, we can appreciate that knowledge, skills, and concepts from both fields can be integrated and synergized to advance biomedical, public health, and population sciences.  

Epidemiology also helps investigate how well specific therapies or other health interventions prevent or control health problems. Because health is multifaceted, epidemiology is interdisciplinary.  The keys to understanding health, injury, and disease are embedded in the language and methods of epidemiology.

The recent emergence of molecular pathological epidemiology (MPE), which represents an integration of population and molecular biologic science to gain insights into the etiologies, pathogenesis, evolution, and outcomes of complex multifactorial diseases. Most human diseases, including common cancers (such as breast, lung, prostate, and colorectal cancers, leukemia, and lymphoma) and other chronic diseases (such as diabetes mellitus, cardiovascular diseases, hypertension, autoimmune diseases, psychiatric diseases, and some infectious diseases), are caused by alterations in the genome, epigenome, transcriptome, proteome, metabolome, microbiome, and interactome of all of the above components. In this era of personalized medicine and personalized prevention, we need integrated science (such as MPE) which can decipher diseases at the molecular, genetic, cellular, and population levels simultaneously

MPE is a recently established interdisciplinary and transdisciplinary field. Traditional epidemiology (including molecular epidemiology and genome-wide association studies) has the substantial limitation of treating pathogenically heterogeneous diseases (e.g., hypertension, diabetes mellitus, major depression, breast cancer) as a single entity. In contrast, from the MPE viewpoint, any human disease entity is fundamentally heterogeneous from person to person, just as each individual is unique. Nonetheless, by classifying disease according to its pathogenic mechanisms, we can better predict the course of a disease in a given individual. In fact, there exists heterogeneity of risk factors as well as heterogeneity of molecular pathogenesis in any given disease.

A growing body of literature (see Web Appendix (http://aje.oxfordjournals.org/)) supports this MPE paradigm, with evidence suggesting that carcinogenic or protective effects of lifestyle, dietary, environmental, and genetic factors differ according to specific molecular characteristics in neoplastic cells. The MPE concept is gaining widespread adoption., MPE studies have improved our understanding of pathogenesis by demonstrating consistent links between etiologic factors and molecular subtypes of diseases. Furthermore, recent evidence suggests that host factors can interact with tumor molecular changes to modify cancer cell behavior. Thus, the MPE approach, unlike the traditional epidemiologic research design, allows insights into etiologic factors and pathogenic mechanisms.