Epidemiological Understanding
Epidemiology is the basic science underpinning public health and clinical medicine. It describes the occurrence of health-related states or events (incidence, prevalence), quantifies the risk of disease (relative risk, attributable risk, odds ratio) and its outcome (prognosis, survival, mortality), and postulates causal mechanisms for disease in populations (aetiology, prevention). The main function of epidemiology is to provide evidence to guide public health policy and clinical practice to protect, restore, and promote health of individuals and populations.
Public health is the collective and organised action by the society to improve the health of populations. This involves collaborative working between doctors, nurses, engineers, environmental scientists, health educators, social workers, nutritionists, administrators, and an effective partnership with non-governmental organisations (NGOs), corporations, and all levels of the government.
The applications of epidemiology in public health and clinical practice can be summarised as follows:
• To describe the spectrum and extent of disease in the population – e.g. what is the prevalence of human papilloma virus (HPV) infection among young girls?
• To identify factors that increase or decrease the risk of disease – e.g. what factors increase the risk of, or protect against, endometrial cancer?
• To study the natural history and prognosis of disease – e.g. does early diagnosis of cervical intraepithelial neoplasia (CIN) through cytological screening prevent future morbidity and improve survival?
• To monitor and predict disease trends in the population – e.g. what impact will the increasing prevalence of obesity in women have on future disease trends and healthcare needs?
• To provide evidence for developing public health policy and making regulatory decisions – e.g. will a smoking ban in public places promote smoking cessation and reduce the incidence of smoking-related disease?
• To evaluate the efficacy of preventive and therapeutic interventions – e.g. does postmenopausal hormone replacement therapy (HRT) do more harm than good?
• To evaluate public health programmes – e.g. will vaccination of schoolgirls against oncogenic HPV prevent vulvar/vaginal/cervical cancers and save lives?
• To evaluate the effectiveness of health services – e.g. are known contacts of persons with sexually transmitted diseases (STDs) followed up and treated?