Epidemiology 101 Final – Flashcards
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Causally (X causes Y variables)
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Causal Association
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(X variable does not cause Y variable)
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Noncausal association
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A graphic plotting of the distribution of cases by time of onset. -Aids in identifying the cause of a disease outbreak.
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Epidemic curve
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Contingency table
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demonstrates associations
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a type of correlative association between an exposure and an effect
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Dose-response relationship
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the lowest dose at which a particular response occurs
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Threshold
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time of initial exposure and the response
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Latency
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is one that has several peaks in the frequency of a condition.
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Multifactorial curve
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involve more than one causal factor ex: Specific exposures (e.g., smoking family history Lifestyle characteristics Environmental influences
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multifactorial casualty
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the category in a frequency distribution that has the highest frequency of cases
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mode
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The process of passing from observations and axioms to generalizations
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inference
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single value (sample-based) chosen to represent the population parameter
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Point estimate
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A range of values that with a certain degree of probability contain the population parameter -Used as an alternative to point estimate
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Confidence interval estimate
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the ability of a study to demonstrate an association, if one exists
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power
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diagram plots two variables, one on the X axis (horizontal) and one on the Y axis (vertical). -The closer the points lie with respect to the straight line of best fit through them (called the regression line), the stronger the association between variable X and variable Y
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Scatter plot
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the assertion that that the observed association is not likely to have occurred as a result of chance
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statistical significance
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Any conjecture cast in a form that will allow it to be tested and refuted.
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Hypothesis
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All of the factors in two or more domains are the same except for a single factor, which is hypothesized to be the "cause" of a disease. Example: differences in coronary heart disease rates between sedentary and nonsedentary workers
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Method of difference
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A type of association in which the frequency of an outcome increases with the frequency of exposure to a factor, the hypothesized cause of the outcome. Example: Dose-response relationship between number of cigarettes smoked and mortality from lung cancer
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Method of concomitant variation
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Refers to the process of defining measurement procedures for the variables used in a study Example: In a study of the association between tobacco use and lung disease, the variables might be the number of cigarettes smoked and the occurrence of asthma.
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Operationalization
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Hill's Criteria of Casualty
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- Strength - Consistency - Specificity - Temporality - Biological gradient - Plausibility
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Strong associations give support to a causal relationship between factor and disease
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Strength
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An association has been observed repeatedly
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Consistency
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Association is constrained to a particular disease-exposure relationship
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Specificity
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The cause must be observed before the effect.
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Temporality
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also known as a dose-response curve; shows a linear trend in the association between exposure and disease.
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Biological gradient
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The association must be biologically plausible from the standpoint of contemporary biological knowledge
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Plausibility
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What is the web of causation used for?
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measure the multiple casualty factors and which one has a higher peak (effect).
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How do epidemiologist account for chance in observed association?
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Epidemiologists employ statistical procedures
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What is the focus of analytic epidemiology?
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- Lead to the prevention of disease - Assist in creation of quantitative evaluations of intervention programs - Aid in determining safety and efficacy of new drugs and other procedures
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Observational design: investigator
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-Does not have control over the exposure factor -Usually is unable to assign subjects randomly to study conditions
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Experimental design: investigator
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-Controls who is exposed to a factor of interest -Assigns subjects randomly to study groups
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Subjects are defined on the basis of the presence or absence of an outcome of interest. -Cases: are those individuals who have the outcome or disease of interest, whereas the controls: do not.
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Case-Control study
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Advantages of a case-control study
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Can be used to study low-prevalence conditions Having a disease is a criterion for being selected as a case. Relatively quick and easy to complete Usually inexpensive Involve smaller number of subjects
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Disadvantages of a case-control study
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Measurement of exposure may be inaccurate Representativeness of cases and controls may be unknown Provide indirect estimates of risk The temporal relationship between exposure factor and outcome cannot always be ascertained.
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is one in which the cases and controls have been matched according to one or more criteria such as sex, age, race, or other variables. -Matching aids in controlling confounding.
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Matched case-control study
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a study in which the units of analysis are populations or groups of people rather than individuals." -Examples of groups are nations, states, census tracts, counties. -May be used when individual measurements are not available, but group-level data can be obtained.
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Ecologic Studies
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Advantages of ecologic studies
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May provide information about the context of health. Can be performed when individual-level measurements are not available. Can be conducted rapidly and with minimal resources.
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Disadvantages of ecologic studies
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Ecologic fallacy Imprecise measurement of exposure
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An erroneous inference that may occur because an association observed between variables on an aggregate (collective) level does not necessarily represent or reflect the association that exists at an individual level;... -ex: Worldwide, richer cities have higher rates of coronary heart disease (CHD) than poorer cities
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Ecologic Fallacy
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defined as a population group, or subset thereof (distinguished by a common characteristic), that is followed over a period of time. Ex: Birth or age cohort Work cohort School/educational cohort
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Cohort study
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Know Differentiate between Prospective and retrospective
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Prospective Cohort Study: Subjects are classified according to their exposure to a factor of interest and then are observed over time to document the occurrence of new cases (incidence) of disease or other health events. Retrospective Study- Makes use of historical data to determine exposure level at some baseline in the past -Follow-up for subsequent occurrences of disease between baseline and present is performed. -Example: a study of mortality among an occupational cohort of shipyard workers employed at a specific naval yard during a defined time interval in the past.
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a measure of the association between frequency of exposure and frequency of outcome used in case-control studies
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Odds ratio (OR) OR = (AD)/(BC)
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OR = (AD)/(BC)
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-An OR ?1 suggests a positive association between exposure and disease. -An OR of 2.1 (about 2) suggests that the odds of disease are about two times higher among the exposed than among the nonexposed. -An OR <1 indicates that the exposure might be a protective factor. -An OR = 1.0 indicates no association between exposure and outcome (not statistically significant).
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the ratio of the incidence rate of a disease or health outcome in an exposed group to the incidence rate of the disease or condition in a nonexposed group -Relative risk = Incidence rate in the exposed / (divided by)
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Relative risk (RR):
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Relative risk = Incidence rate in the exposed / (divided by) Incidence rate in the nonexposed
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The relative risk (RR) = [A/(A + B)] ÷ [C/(C + D)]
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in a cohort study, refers to the difference between the incidence rate of a disease in the exposed group and the incidence rate in the nonexposed group. -Estimates realistic potential of an exposure causing an outcome by removing that exposure from the population
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Attributable risk:
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refers to "A research activity that involves the administration of a test regimen to humans to evaluate its efficacy and safety....
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Clinical trial
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participants may be switched between treatment groups
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crossover design
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an intervention designed for the purpose of -educational and behavioral changes at the population level. -Most community interventions use quasi-experimental designs
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community intervention (community trial)
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a type of research in which the investigator manipulates the study factor but does not assign individual subjects randomly to the exposed and nonexposed groups.
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quasi-experimental study
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Refers to one's ability to generalize from the results of the study to an external population
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External validity
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Refers to the degree to which the study has used methodologically sound procedures.
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Internal Validity
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A type of error that arises when values (statistics) obtained for a sample differ from the values (parameters) of the parent population
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Sample Error
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Cases may remember an exposure more clearly than controls.
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Recall bias
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"Distortions that result from procedures used to select subjects and from factors that influence participation in the study...."
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Selection bias
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List 3 ex's of outcome variables of an ecologic study:
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-specific cause mortality ex: breast cancer -all cause mortality ex: heart disease -morbidity ex: occupational injuries
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What is the purpose of random assignment?
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controls for many of the factors that effect study designs, including assignment of exposures and biases in assessment of study outcomes
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What is meant by the term confounder?
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a third variable that was not considered in the study design, that affected the association between the exposure and outcome which leads to invalid conclusions.
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Describe a randomized control trial?
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an epidemiological experiment in which subjects in a population are randomly allocated into groups, usually called study and control groups, to receive or not to receive an experimental preventive or therapeutic procedure, maneuver or intervention.
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Be familiar with 7 factors that characterize study designs.
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Who manipulates the exposure factor? How many observations are made? What is the directionality of exposure? What are the methods of data collection? What is the timing of data collection? What is the unit of observation? How available are the study subjects?
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is defined as the presumptive identification of recognized disease or defects by the application of tests, examinations, or other procedures that can be applied rapidly.
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Screening for disease
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Screening for disease Provides:
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provides only preliminary information: a diagnostic confirmation of any positive results of a screening test is required
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Refers to the ability of a measuring instrument to give consistent results on repeated trials. Synonym: precision
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Reliability
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The ability of the measuring instrument to give a true measure of the entity being measured Synonym: accuracy
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Validity
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Reliability Versus Validity
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-A screening test should be both reliable and valid. -Reliability and validity are interrelated terms. -It is possible for a measure to be invalid and reliable, but not valid and unreliable. -Example (invalid, reliable): A bathroom weight scale that consistently gives the incorrect weight provides a reliable, but invalid measurement.
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The ability of the test to identify correctly all screened individuals who actually have the disease.
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Sensitivity= a/(a + c)* = 177/244 = 72.5%
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The ability of the test to identify only nondiseased individuals who actually do not have the disease
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Specificity= a/(a + c)* = 177/244 = 72.5%
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the proportion of individuals screened positive by the test who actually have the disease
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Predictive Value (+)= a/(a + b) = 177/445 = 39.8%
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an analogous measure for those screened negative by the test
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Predictive Value (?)= d/(c + d) = 961/1,028 = 93.5%
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is a condition that impairs functioning in the social, communication, and behavioral domains
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Autism (autism spectrum disorder-ASD)
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-Generally appears by 3 years of age -Manifested by difficulties in: -Cognitive functioning -Learning -Processing sensory information -Prevalence in U.S. about 4.5 to 9.9 per 1,000 children
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Autism (autism spectrum disorder-ASD)
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Stressors (sources of stress) that arise from happenings such as job loss, financial problems, and death of a close family member
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Stressful Life events
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Examples: graduation from school, marriage, and birth of a new child
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Positive life events
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are those associated with adverse life circumstances. Examples: being fired from work or being arrested and incarcerated
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Negative life events
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Life events that are sustained over a long period of time
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Chronic strains
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Refers to help received from other people when one is under stress. -Friends, relatives, and significant others often are able to provide material and emotional support during times of stress.
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Social support
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an anxiety disorder that some people develop after seeing or living through an event that caused or threatened serious harm or death....
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Posttraumatic stress disorder
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Symptoms of Posttraumatic stress disorder
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Flashbacks or bad dreams Emotional numbness Intense guilt or worry Angry outbursts Feeling 'on edge' Avoiding thoughts and situations that remind them [people] of the trauma
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Social epidemiology vs. behavioral epidemiology
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Social epidemiology - the discipline that examines "...the social distribution and social determinants of states of health." VS. Behavioral epidemiology - defined as the study of the role of behavioral factors in health.
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Studies the occurrence of mental disorders in the population -Variables include age, sex, and social class. -The discipline measures the frequency of occurrence of mental disorders and factors related to their etiology. -DSM-IV-TR (2000)- Manual used for the classification of psychiatric disorders
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Psychiatric Epidemiology
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- The choice of behavioral factors that affect how we live -These choices often are a function of social influences. -Personal behavior is associated with many chronic diseases. -The impact of the factors is not fully recognized
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Lifestyle
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- a physical, chemical, or emotional factor that causes bodily or mental tension and may be a factor in disease causation
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Stress
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Examples of conditions studied as outcomes of stress:
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- Cardiovascular disease - Post-traumatic stress disorder - Work-related anxiety and neurotic disorders
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What are some of the health effects studied in relation to stress?
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Types of mental disorders - Anxiety disorders - Mood disorders Major depressive episode Dysthymia Bipolar disorder - Impulse control disorders - Substance abuse disorders
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A condition that contributes to decay and loss of teeth Attributed to: -Reduced output of saliva -Increased sugar consumption -Neglect of personal hygiene
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Meth mouth
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the co-occurrence of two or more mental disorders - For example, major depression and substance use disorder
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Psychiatric comorbidity
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Be familiar with illicit drugs that are commonly abuse in the U.S states:
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-Marijuana- The most commonly used illicit drug among persons aged 12 or older (2006) -Methamphetamines -Heroin -Other abused drugs include: Prescribed painkillers
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Social and behavioral dimensions that impact human health.
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Tobacco use, excessive alcohol consumption -Substance abuse -Sedentary habits -Stress
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Potential consequences of global warming
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-Northward movement of disease-carrying arthropods (e.g., mosquitoes) -Melting glaciers -Extreme climatic conditions such as heat waves
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used...in reference to susceptibility genes."
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Genetic marker
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Genetic marker of susceptibility
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-When these genes are present, the person may have increased susceptibility to specific exposures. -An example is the linkage between the gene CYP2D6 and susceptibility to the effects of exposure to benzoapyene, a hazardous chemical.
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Molecular epidemiology uses molecular markers in addition to genes to establish exposure-disease relationships. Select one: True False
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True
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A physical, chemical, or emotional factor that causes bodily or mental tension and may be a factor in disease causation is: a. Positive life events b. Negative life events c. Genetic predisposition d. Risk factors e. Stress
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Stress
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Lung cancer is the leading cause of cancer death for both men and women in the United States. Select one: True False
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True
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A host factor that enhances some step in the progression between exposure and disease such that the downstream step is more likely to occur is known as a: a. Genetic marker of susceptibility b. Forensic mutation c. Genetic mutation d. Forensic marker of susceptibility e. Genetic predisposition
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Genetic marker of susceptibility
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Certain genes can be markers for susceptibility but do not confer risk on their own. Select one: True False
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True
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An anxiety disorder that some people develop after seeing or living through an event that caused or threatened serious harm or death is known as: Select one: a. Bipolar disorder b. Autism c. Posttraumatic stress disorder d. Major depressive disorder e. Clinical depressive disorder
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Posttraumatic stress disorder
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All of the following are examples of diseases known or believed to have a genetic basis EXCEPT: Select one: a. Chlamydia b. Downs syndrome c. Tay-Sachs disease d. Hemophilia e. None of these choices are correct
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Chlamydia
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Life events that are sustained over a long period of time are known as: Select one: a. Risk factors b. Catastrophic events c. Chronic strains d. Stressful life events e. Social events
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Chronic strains
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The choice of behavioral factors that affect how we live is known as: Select one: a. Coping skills b. Resources c. Lifestyle d. Chronic strains e. Social support
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Lifestyle
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Global warming is a controversial topic that refers to the gradual decrease in the earth's temperature over time. Select one: True False
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False
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Contingency tables tabulate data according to two dimensions. Select one: True False
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True
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Analytic epidemiologic studies focus on causal associations between exposures and outcomes. Select one: True False
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True
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An erroneous inference that may occur because an association observed between variables on an aggregate level does not necessarily reflect the association at an individual level is known as an: Select one: a. Odds Ratio b. Ecologic Correlation c. Ecologic Fallacy d. Relative Risk e. Confidence Interval
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Ecologic Fallacy
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The process of passing from observations and axioms to generalizations is known as: Select one: a. Inference b. Point Estimation c. Power Testing d. Confidence Intervals e. Statistical Significance
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Inference
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With respect to derivation of hypotheses, a situation in which all of the factors in two or more domains are the same except for a single factor is known as: Select one: a. Method of concomitant variation b. Operationalization c. Method of difference d. Analytic Epidemiology e. Descriptive Epidemiology
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Method of difference
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Participants are classified according to their exposure to a factor of interest and then are observed over time to document the incidence of disease in what type of study? Select one: a. Prospective Cohort Study b. Case-Control Study c. Cross-Sectional Study d. Retrospective Cohort Study e. Historical Prospective Study
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Prospective Cohort Study
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Examples of categorical variables are height and weight. Select one: True False
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False
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Ecologic studies use the group as the unit of analysis rather than the individual. Select one: True False
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True
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A type of variable that can have an infinite number of values within a specified range is: Select one: a. Continuous b. Positive c. Negative d. Concomitant e. Categorical
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Continuous
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Random assignment of subjects to study groups helps to control for: Select one: a. Directionality of Exposure b. Biases Due to Confounding c. Timing of Data Collection d. Blinding e. Stratification
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Biases Due to Confounding
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Molecular epidemiology vs. genetic epidemiology
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Molecular epidemiology - A subfield of epidemiology that uses molecular markers in addition to genes to establish exposure-disease relationships VS. Genetic epidemiology - has a narrower focus than molecular epidemiology. -It is concerned with "...the identification of inherited factors that influence disease, and how variation in the genetic material interacts with environmental factors to increase (or decrease) risk of disease."
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-Examples of conditions that are known or believed to have a genetic basis are:
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Hemophilia Tay-Sachs disease Sickle cell disease BRCA1 and BRCA2 genes Down Syndrome Congenital malformations
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Refers to the study of diseases and conditions (occurring in the population) that are linked to environmental factors
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Environmental epidemiology
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ocuses on adverse health outcomes associated with the work environment
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Occupational epidemiology
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