Epidemiology is the study of health-related states or events in specific populations and their determinants, with the aim of controlling health problems. It encompasses various research fields, such as cancer epidemiology, infectious disease epidemiology, and social epidemiology, molecular epidemiology, environmental epidemiology, genetic epidemiology, clinical epidemiology, pharmacoepidemiology, spatial epidemiology, and theoretical epidemiology, among others, and is closely related to statistics and biometrics. In analytical epidemiological studies, data is collected from study populations using appropriate study designs, and statistical methods are applied to understand disease occurrence and its causes, particularly establishing causal relationships between interventions or exposures and disease outcomes. This paper focuses on five topics in epidemiology, including infectious disease control through spatial epidemiology, cancer epidemiology using cancer registry data, research about long-term health effects, targeted learning in observational studies, and that in randomized controlled trials. This paper provides the latest insights from experts in each field and offers a prospect for the future development of quantitative methods in epidemiology.
