The WHO book "Basic Epidemiology" by Bonita, Beaglehole, and Kjellström is a foundational text in the field, widely used for teaching basic epidemiological principles. It covers various quantitative study designs, and its advice is highly relevant to the Ethiopian context, given the country's public health challenges and the need for evidence-based interventions. The book typically discusses the following basic quantitative study designs:
Descriptive Studies:
Purpose: To describe the occurrence of disease or health-related states in terms of person, place, and time. They answer "who, what, where, when."
Types:
Case Reports and Case Series: Detailed reports of individual cases or a small group of cases with unusual or new diseases/conditions.
Ecological (Correlational) Studies: Examine the relationship between exposure and disease in populations, rather than individuals.
Cross-sectional Studies: Measure both exposure and outcome simultaneously in a defined population at a specific point in time. They provide a snapshot of the prevalence of disease and exposure.
Relevance to Ethiopia:
High: Descriptive studies are crucial in Ethiopia for understanding the burden of disease, identifying high-risk groups, and tracking trends. For instance, cross-sectional surveys (like Demographic and Health Surveys - DHS, or specific surveys on malnutrition or disease prevalence) are extensively used to provide national and regional estimates. My lead poisoning project, aiming to determine prevalence, is a cross-sectional study. Case reports/series can highlight emerging or unusual health problems.
Analytical Studies (Observational):
Purpose: To test hypotheses about cause-and-effect relationships by examining associations between exposures and outcomes. They answer "why" and "how."
Types:
Case-Control Studies: Compare a group of individuals with a disease (cases) to a group without the disease (controls) to determine past exposures that might be associated with the disease.