A Textbook of Community Medicine/Medical Epidemiology

According to John M Last, Epidemiology is the study of the distribution and determinants of health-related states and events in specified populations and application of this study to the control of those health problems.

It is a scientific, systematic and data driven study of all health related states or events, not disease alone. Distribution of health related states in terms of time, place and person are studied. In other terms when and where the health related states occur and what are the characteristics of those affected. Magnitude of those health related states or events in terms of incidence and prevalence are studied. Determinants of the health related states and events include causes and risk factors of those conditions. Findings of the study is applied in controlling those health related states or events.