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Karteikarten von Ashutosh Kumar, aktualisiert more than 1 year ago
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| Incidence: Definition: Incidence rate: Elements of incidence rate: Reasons for change in incidence: Uses of incidence: | Incidence: The number of new cases of disease in the population during a specified time period. Incidence rate: The number of new cases in the population during a specified time period, divided by the number of persons at risk (or person time) of developing the disease during that time period. Incidence rate measures the speed at which new cases are occurring in the population within a time period. Incidence rate consists of 3 essential elements; number of new cases (numerator); person time (denominator); time. Incidence rate is expressed in a particular convention e.g number of cases per 100,000. Increase in incidence: immigration of susceptible persons, change in diagnostic criteria, improved case ascertainment, introduction of a new diagnostic/screening test, introduction of new, or changes in exposure to existing etiologic agent(s). Used to predict risk of disease, research causes of disease, describe trends of disease over time and evaluate effectiveness of prevention programmes. |
| Prevalence: Definition: Types: Elements of prevalence: Reasons for change: Uses: | Prevalence: The number of existing cases of disease in a defined population at a notional point in time (point prevalence) or at any time during a certain period (period prevalence), divided by the number of person in the population at that time. Prevalence is a measure of the extent of the health problem or burden of disease in the population, expressed as a proportion. Prevalence depends on the incidence and the duration of the disease. Increased prevalence of disease in the population can be due to: in migration of cases, increase in incidence, and/or longer duration of disease. Collected from cross-sectional studies and surveys. Prevalence data is used for planning health services, resource allocation and organization of prevention programmes. |
| Ecologic studies: What: Why: Outcome measure: Advantages: Disadvantages: | Ecologic studies: What: Examine the association between exposure and occurrence of disease with population level data. Why: Excellent at generating hypotheses. Outcome measure: Correlation coefficient Advantages: Quick to conduct if routine data on exposure and disease available Inexpensive Useful for examining effect of short term variations in exposure within the same population and evaluating impact of public health intervention by comparing aggregate-level information before and after the intervention Disadvantages: Subject to confounding as information on potential confounders is generally not available Ecological fallacy; associations at the population level do not necessarily represent associations at the individual level. Cannot establish causality. |
| Correlation studies: What: Why: Advantages: Disadvantages: | Correlation studies: What: Determine the prevalence of an exposure and/or disease in a defined population at one particular time. Why: Determine the burden of exposure and/or disease in the population, assess knowledge, attitude, and practice in relation to health-related issues, public health monitoring, and planning interventions and health services, and to generate hypotheses and examine the association between exposure and disease. Advantages: Can examine multiple exposures and outcomes simultaneously in each individual. Can be conducted in a relatively short time. When based on a representative sample, their findings can be generalized to the whole population. Sequential health surveys are the best method for monitoring trends in behavioural/lifestyle risk factors over time. Disadvantages: Not possible to establish a temporal sequence between exposure and disease. |
| Case-control studies: What: Why: Outcome measure: Advantages: Disadvantages: | Case-control studies: What: Study associations of disease with an exposure or factor; subjects are defined as cases (persons with disease) and controls (persons without disease), and past exposure and/or biologic markers are compared. Why: Generate and test etiologic hypotheses, evaluation of screening and prevention programmes, vaccine and treatment efficacy, and outbreak investigation. Outcome measure: Odds ratio Advantages: Can study association of a disease with several exposures and characteristics, and measure potential confounding factors. Relatively inexpensive and conducted in a short time Efficient for rare disease and those with a long induction/latent period. Disadvantages: Subject to problems with control selection and matching between cases and controls Recall bias Sometimes difficult to establish a clear temporal sequence between exposure and disease Inefficient for rare exposures |
| Cohort studies: What: Prospective cohort: Retrospective/historic: Why: Outcome measure: Advantages: Disadvantages: | Cohort studies: Wha: Study associations of an exposure with a disease and/or several health outcomes; participants are grouped according to exposure (exposed/unexposed) and followed over time to compare the incidence of health outcomes. Prospective cohort: Retrospective/historic: Why: To test etiologic hypotheses, understand physiology, pathogenesis, prognosis, and natural history of disease, and evaluation of screening and prevention programmes and vaccine and treatment efficacy. Outcome measure: Incidence rates, from these, RR, AR and PAR. Advantages: Possible to establish temporal sequence Possible to study associations of an exposure with multiple outcomes, and also to study multiple exposure. Less vulnerable to bias since exposure (baseline) established at the start of the study and the outcomes have not occurred. Historic studies take less time and money to conduct Disadvantages: Relatively expensive Take a long time to yield results Inefficient for studying rare outcomes. >10% loss to follow up can undermine validity of study In historic studies data available may be inade |
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