Introduction to Epidemiology Studies PDF

Introduction to Epidemiologic Study Design Dr Muhammad Ahmed Alshyyab Lecture 1 week Chapter 5 Lecture objective To clarify causal relations between various determinants (‘‘exposures’’) and health outcomes in order to generate a Hypothesis st...

Introduction to Epidemiologic Study Design Dr Muhammad Ahmed Alshyyab Lecture 1 week Chapter 5 Lecture objective To clarify causal relations between various determinants (‘‘exposures’’) and health outcomes in order to generate a Hypothesis statement To understand the ethical conduct of studies involving human subjects Etiologic research Hypotheses are nets: only he who casts will catch. Novalis Hypothesis statement An odd case report. Descriptive epidemiologic studies. As hypotheses are generated and refined, Detailed studies follow, perhaps end with in an epidemiologic experiment. The need to have sharply focused research questions and hypotheses. The study must then be designed in a manner that will Elements of an epidemiologic hypothesis 1. The population 2. The exposure. 3. The disease. 4. The induction period. 5. The expected change in incidence. 6. Cofactors (potential confounders). 7. The causal mechanism 8. The sample size. Illustrative Example for Elements of an epidemiologic hypothesis The hypothesis is does the estrogen dose in COCs is related to VTE risk. Population: Women (15 - 44 years old) using oral contraceptive. Exposure: The exposure COCs ≥ 50μg of estrogen, nonexposed COCs ≤ 35μg of estrogen. Disease: The confirmed diagnosis of VTE and its treatment. Induction period: ‘current use.’ Expected change in incidence: cut the incidence of VTE from 8/10 000 to 4/10 000 person-years. Cofactors: age, recent surgery, trauma, the post-partum period. Mechanism: Exogenous estrogen is increase thrombogenesis and decreases fibrinolysis. Sample size: A study of 60,000 women. Variables Exposure E → Disease D? Independent variable in statistical analyses. Dependent variable in a statistical analysis Potential confounders, control variables, extraneous variables, or cofactors. Data Examples of data sources include: 1. interviews with study subjects 2. self administered questionnaires 3. employment records 4. environmental records 5. health care records 6. social services records 7. physical examination 8. examination of biological specimens 9. and various types of diagnostic tests. Ethical conduct of studies involving human subjects Institutional review boards (IRBs) IRBs are committees composed of researchers, clinicians, administrators, and laypeople who review the study protocol before the study is begun. Their primary objective is to ensure the ethical treatment of human subjects and to oversee informed consent procedures. Equipoise Equipoise is ‘‘balanced doubt’’ about the pros and cons of the intervention Treatments that present special hazards cannot be ethically assigned Treatments that are believed to be beneficial cannot be ethically withheld. Data and Safety Monitoring Board (DSMB). The DSMB is an independent group of outside experts that periodically reviews and evaluates accumulated evidence from the study to monitor its safety and progress. The job of the DSMB is to make recommendations concerning the continuation, modification, or termination of the study.