HS 2801 Notes (Week 6) PDF

Week 6 Design 1 2 types of population/clinical health research - Descriptive: identify and count cases of disease in population according to person, place, time, and conduct simple studies - Case reports and series - Cross sectional - Ecological...

Week 6 Design 1 2 types of population/clinical health research - Descriptive: identify and count cases of disease in population according to person, place, time, and conduct simple studies - Case reports and series - Cross sectional - Ecological 1. Monitor public health 2. Evaluate the success of intervention programs 3. To generate hypotheses about the causes of disease - Analytic: compare group and systematically determine if there is an association - Experimental study (clinical trial and community trials) - Case control - Cohort study 1. Evaluate hypothesis about the causes of disease 2. Evaluate the success of intervention programs Goals and design decisions - Conduct health research study to determine the relationship between exposure of interest and a disease/outcome of interest with validity and precision using the least amount of resources - How should u define exposure - In which people - How should u define your disease - How can you make study valid - Random error - Bias - Confounding - How can you make study efficient - Time - Money Components of a study 1. Population - Source population: the population you are interested in knowing about - Study population: the population you enrol to represent the source population - Generalizability: assuming the association in study truly reflects the truth, to whom does it apply? Must be internally valid 2. Exposure - Exposure: determinant of interest upon which an outcome depends, can be constitutional, environmental, or behavioural 3. Outcome - Case definition: description of the event you are interesting in studying, can be disease, defect, injury, state or event - Man with cardiovascular disease defined by ICD codes - A woman with first occurrence of breast cancer identified in a cancer registry - An infant with a structural abnormality of the heart identified within the first week of life 4. Potential confounders - Confounder: extraneous risk factor for an outcome, can be constitutional, environmental or behavioral - Leads to distortion of true association between exposure and disease - Goal is to identify and control them 5. Analysis - Examination of study data, estimation of measure of disease frequency - Describe study pop (proportions, rates, exposures) - Crude estimates - Adjusted estimates - Standardized - Stratified analysis - Multivariate analysis 6. Communication of findings - Tell appropriate person or community what you found even if you had no association - Peer reviewed journal - Conferences and meetings - Government reports - Social media Case report and series - Case report: a report of one health issue in one patient - Disease, disorder, undergoing a procedure - Case series: a report that describes a group of people who have the same health issue - There's no theory, no research question, no research, only reporting - May generate ideas for research - Main scientific part: defining the case - Based on list of inclusion and exclusion criteria individuals will be classified as case (diagnosed) - Sign: elevated indication of disease that can be clinically observed, ex: rash, cough, fever, high bp - Symptom: a subjective indication of illness that is experiences by an individual but can not be directly observed by others - Several coding systems - International classification of disease - Diagnostic and statistical manual of mental disorders - Mostly in medical settings, but data collection is done with questionnaires - Ethical issues should be respected - Privacy - Labeled unjustly because of original case series - Few or not data analysis is required - Clinical discussion dominates the report How to decide on study design - Types of analytical studies - Experimental: investigator actively manipulated groups receive agent under study - Community and clinical trials - Observational: investigator observes as nature takes its course - Cross sectional - Cohort - Case control Cross sectional studies (prevalence) - A group of people are examined at one point in time - Prevalence: the percentage of members of a population who have a given health issue at the time of the study - Point prevalence: proportion of prevalence with particular illness at one point in time - Period prevalence: proportion of prevalence with particular illness during a defined time period - Prevalence rate ratio (relative risk in cross sectional studies) - A comparison of the prevalence of a characteristic in 2 independent population (or independent subpopulations) that is calculated by taking ratio of prevalence rates - PR = (a/(a+b)/(c/c+d) - Urban vs rural pop - Exposed vs unexposed Limitation of cross sectional - No time dimension - Can not be used to assess causality - An exposure can be said to be associated or related to disease, but cross sectional study can not show that an exposure caused a disease - Repeated cross sectional study: a series of cross sectional studies that re sample and re survey representative from the same source population at two or more different time points - Does not track the same individuals - A new set of participants is sampled from the source population for each round of data Correlational (ecological studies) - The unit of analysis is the group, not the individual - The group, ecological unit represents an aggregate of individuals - Variable in correlational studies are usually aggregate statistics such as the proportion of a population with a particular characteristics or the average value of the variable in a population - Comparing something between groups Ecological fallacy - Fallacy: a mistaken belief, especially one based on unsound argument - The incorrect assumption that individual will follow the trends observed in a population level data, not a methodological error or bias - The experience of individuals in a population may vary significantly from the population average - The results of ecological studies should be interpreted with extra caution