Descriptive Study Designs - Health - Lecture Slides, Slides of Public Health

Download Descriptive Study Designs - Health - Lecture Slides and more Slides Public Health in PDF only on Docsity! Descriptive Study Designs • POPULATIONS (GROUPS) --- Ecologic (aggregate) studies • INDIVIDUALS --- Case reports --- Case series --- Cross sectional surveys docsity.com Ecologic Studies • Measures that represent characteristics of entire populations are used to describe disease and to postulate causal associations. • Measure of interest is correlation between exposure rates and disease rates among different groups. • Correlation coefficient (denoted as r) Range of r is from –1.0 to 1.0 R evaluated in relation to difference from 0. docsity.com Ecologic Studies The “Ecologic Fallacy”: • Erroneous conclusions based on grouped data • Patterns observed on the aggregate level are not observed on the individual level docsity.com 0 10 20 30 0 0.2 0.4 0.6 0.8 1 Suicide Rate per 100,000 Proportion Protestant In 1951, Durkheim, reported an association between the rate of suicide and proportion of four Prussian provinces of Protestant religion. How might the ecologic fallacy be responsible for this association? docsity.com 0 10 20 30 0 0.2 0.4 0.6 0.8 1 Suicide Rate per 100,000 Proportion Protestant As non-Protestants in each province became more in the minority, these individuals, rather than Protestants, may have been more likely to commit suicide. docsity.com Case Series (individual data) • Description of clinical/epidemiologic characteristics of a number of patients with a given disease • Collection of individual case reports occurring within a fairly short period of time docsity.com Case Series Strengths: • Used as an early means to identify the beginning or presence of an epidemic • Can suggest the emergence of a new disease (i.e. AIDS) docsity.com Case Series Limitations: • Lack of an appropriate comparison group • Cannot be used to test for presence of a valid statistical association • Not a true epidemiologic design docsity.com Cross-Sectional Studies 45050 Normal/ Low 400100High No CHDCHD Cholesterol 100 / (100 + 400) 0.2 Prevalence Ratio = --------------------- = ---- = 2.0 50 / (50 + 450) 0.1 docsity.com Cross-Sectional Studies 100 / (100 + 400) 0.2 Prevalence Ratio = --------------------- = ---- = 2.0 50 / (50 + 450) 0.1 Interpretation: In this study population, the prevalence of CHD is 2 times higher among those with high cholesterol, compared to the prevalence in those with normal or low cholesterol. docsity.com Cross-Sectional Studies Strengths: • Provides prevalence estimates of exposure and disease for a well-defined population • Easier to perform than studies that require follow-up (hence relatively inexpensive) • Can evaluate multiple risk (and protective) factors and health outcomes at the same point in time docsity.com National Surveys • A large set of national epidemiological surveys are conducted by the National Center for Health Statistics (NCHS) --- the Federal Government’s principal vital and health statistics agency. • The NCHS is part of the Center for Disease Control and Prevention (CDC) – under the U.S. Dept. of Health and Human Services. docsity.com National Surveys • National Health Interview Survey (NHIS) Principal source of information on the health of the civilian, non- institutionalized household population of the U.S. • National Health and Nutrition Examination Survey (NHANES) Collects information about the health and diet of people in the U.S. docsity.com National Surveys • National Health Care Survey (NHCS) Collects a wide range of data on health care use, impact of medical technology, and quality of care provided. • National Immunization Survey (NIS) Collects information on the immunization coverage and health care of children across the U.S. docsity.com National Surveys/Programs • Youth Risk Behavior Surveillance System Collects data to monitor prevalence of behaviors in youths that results in significant mortality, morbidity, disability, and social problems. • National Program of Cancer Registries (NPCR) • Surveillance, Epidemiology, and End Results (SEER) Program docsity.com Other Sources of National Data • National Vital Statistics System --- Birth data --- Mortality data --- Fetal death data --- Marriages and divorces --- Linked births/infant deaths --- National death index • U.S. Census Bureau docsity.com