Final answer:
Epidemiology's scope has expanded from focusing solely on infectious diseases to including non-infectious diseases, environmental and behavioral health factors. Significant advancements have occurred due to improved public health measures, behavioral changes, and medical interventions, contributing to increased life expectancy and better management of diseases.
Step-by-step explanation:
The theories and practices of epidemiology have undergone significant changes over the last century. Epidemiology has evolved from primarily investigating epidemics of infectious diseases to encompassing non-infectious diseases and environmental and behavioral factors related to health. Early figures such as John Snow and Florence Nightingale laid the foundation by using disease pattern analysis. This evolved with the acceptance of the germ theory, propelling microbiology and public health policies forward. Richard Doll and Austin Bradford Hill's mid-1900s studies on the links between tobacco smoking and lung cancer highlighted the role of epidemiology in noninfectious diseases.
In the modern era, advances in public health measures, such as improved sanitation and vaccination, and changes in behavior, like smoking reduction and hand hygiene, have played a significant role in increasing life expectancy. Moreover, the discovery of antibiotics and medications for chronic conditions like hypertension further contributed to controlling diseases and extending longevity. This transformation showcases epidemiology's vital role in public health and population-based health management.