Unit 1 - Definitions and Equations Flashcards

Question

Latency Period

Answer 1

Time between onset of disease and disease diagnosis

Answer 2

= # live births / 1,000 population

Answer 3

= # deaths of women while pregnant or within 42 days of termination of pregnancy / 100,000 live births

Answer 4

Any departure, subjective or objective, from a state of physiological or psychological wellbeing - disease, injury, disability Measures characterize the number of persons in a population who become ill (incidence) or are ill at a given time (prevalence)

Answer 5

Death of an individual from any cause

Answer 6

Neonatal period = birth - 28 days old | = # deaths of children under 28 days old / 1,000 births

Answer 7

Higher than normal frequency of disease in a localized population compared to baseline values Occurs on small scale than epidemic Interchangeable with cluster

Answer 8

When an epidemic spreads to cross geographic borders Multi-national, Multi- continent Determined by intensity of spread, multi-continent, and lethality

Answer 9

Ability to cause clinical disease | = # with clinical disease/ # infected

Answer 10

Prevalence measures over specific time period (usually mid year)

Answer 11

Generally calculated from a long-term cohort study Assumes probability of disease during study period is constant Allows us to standardize population when we don’t know the population size or the time period

Answer 12

Postnatal period = 28 days - 1 year | = # deaths of children aged 28 days - 1 year / 1,000 live births

Answer 13

Proportion of people in a population who have a particular disease or attribute at a specified point in time or over a specified period of time Includes all cases - new and preexisting See for people who have a condition during a period of time Used for measuring chronic disease Measure of how much - burden of disease

Answer 14

Proportion of the population that has a health condition at a point in time

Answer 15

Proportion of people with a particular disease or attribute on a particular date Prevalence measured at a particular point in time

Answer 16

Comparison of 2 related things Represents a part of a whole Have to factor numerator into denominator

Answer 17

Proportion of deaths in a specified population over a period of time attributable to different causes = # of cause- specific deaths / total # deaths in population

Answer 18

Comparison of 2 things over time or a specified time period Like a proportion but it must include time Part over whole over time period

Answer 19

Comparing 2 non-related things | Numerator and denominator are separate

Answer 20

Another term for incidence or attack rate

Answer 21

Looks at the difference between community transmission of illness vs transmission of illness in a household/ other closed populations = # of cases among contacts of primary cases / total number of contacts

Answer 22

Case that epidemiologist’s retrospectively label as the first incidence of disease - look at max incubation period and min incubation period Where we link start/ spread of disease to Cannot always be defined as 1 person - sometimes it is a range or nonexistent Depends on illness and nature of contact with others

Answer 23

Going out into the community and asking questions and looking for new disease/ cases More involved - need a lot of time, people, and resources Need to ask questions, conduct research, observe people you are looking at Ex: John Snow and Broad Street Pump

Answer 24

Health care providers have to alert the CDC/ NNDSS when they see a certain disease Passive bec they wait for updates from health care providers and then enter information into database - no boots on ground Let’s us track disease frequency and occurrence over time and within populations

Answer 25

Another form of passive surveillance Used when person presents a certain set of symptoms but a definitive diagnosis cannot be given at moment. Use already defined similar diagnosis to guide decisions and protocol until something more definitive can be done Almost- could be phenomenon

Answer 26

Ability to cause death (case fatality rate) | = # deaths / # with infectious disease

Answer 27

Father of Epidemiology Recognized a lot of people in a London neighborhood were sick. He conducted descriptive EPI by going into community and asking questions and keeping track of his information on a map. He traced the bad water which was leading people to develop/ spread cholera to the Broad Street Pump

Answer 28

A public health basic science that studies the distribution and determinants of health related states and events in specific populations to control disease and illness and promote health

Answer 29

Identify patterns / trends Determine extent Study natural course Identify causes of or risk factors for Evaluate effectiveness of measures Assist in developing public health policy Looking to affect changes on population level

Answer 30

1. Disease occurrence is not random 2. Systematic investigation of different populations can identify associations and causal/ preventive factors and impact changes on health of population 3. Making comparisons is the cornerstone of systematic disease assessments/ investigations

Answer 31

``` Frequencies of disease occurrence - counts of disease - counts of disease in relation to size of population Patterns of disease occurrences - Person (Who) - Place (Where) - Time (Where) = Descriptive EPI ```

Answer 32

Person, Place, Time Who, Where, When Can be used to know if a location is experiencing disease occurrence more frequently than usual for that locale or other locations

Answer 33

Factors of susceptibility/ exposure/ risk Etiology/ causes of disease Modes of transmission Social / Environmental / biological elements that determine the occurrence/ presence of disease Looks at associations vs causes = Analytic EPI

Answer 34

``` Surveillance Field Investigation Analytic Studies Evaluation Linkages Public Policy ```

Answer 35

Portray ongoing patterns of disease occurrence so investigations, control, and prevention measures can be developed and applied Skills: data interpretation - designing and using data collection instruments - data management - scientific writing and presentation

Answer 36

Determine source/ vehicle of disease; to learn more about the natural history, clinical spectrum, descriptive EPI (WWW), and risk factors of a disease

Answer 37

Advance the information generated by descriptive EPI techniques Hallmark of analytic studies is use of comparison group Skills: design, conduct, analysis, interpretation, and communication of research study data and findings

Answer 38

Systematically and objectively determine relevance, effectiveness, efficiency, and impact of activities

Answer 39

Collaborate/ communicate with other public health and health care professionals and the public themselves

Answer 40

Provide input, testimony, and recommendations regarding disease control and prevention strategies, reportable disease regulations, and health care policy

Answer 41

Stage of Susceptibility - environmental, biological, or other Stage of Subclinical disease - body knows you have something but you are pre-diagnosis/ asymptomatic - subclinical = asymptomatic - things are advancing physiologically / pathological changes - induction period = time between exposure and onset of disease Stage of clinical disease - patient and doctor know that disease is presence; may know diagnosis - latency period = time between onset of symptoms and diagnosis Stage of recovery, disability, or death

Answer 42

Epidemic that alerts the world to the need for high vigilance Stage between epidemic and pandemic

Answer 43

Graphical, time based depiction generated during an outbreak/ epidemic reflecting number of cases by date Represents epidemic frequency change over time Incorporates all 3 elements of descriptive EPI

Answer 44

``` Magnitude and Timing of Disease Occurrence - how quick progression is - speed and intensity of disease - sentinel case/ peak/ outliers - start/ stop/ duration Patterns of disease occurrence - shape - Common/ point source - Propagated ```

Answer 45

Not person to person spread Can be continuous (not repeated) or intermittent (repeated) Disease is derived from a common, single point source for outbreak May or may not have index case

Answer 46

Person to person spread Outbreak is spread as infected subjects infect others (secondarily) who then infect others See start to disease and then saw toothing up and down

Answer 47

When have min / max, you can look back to determine range of onset - need to know what illness you are working with When look at max, min, and avg incubation time, you can determine the probable exposure period (range)

Answer 48

1. Number of people affected/ impacted (frequency/ count) 2. Size of the source population (from which disease cases or outcomes arose) or those at risk 3. length of time the ‘population’ is followed - frequency is more more likely to occur at time inc

Answer 49

Exposure to disease, treatment, medicine

Answer 50

Resulting in disease or another health related event

Answer 51

Describes the illogical best way to compare groups - impossible In same group, all else being equal, looks at the outcome if the exposure didn’t occur - pretend like the exposure didn’t occur - ex: smoker’s risk of Coronary Heart Disease - Would pretend that they got CHD but not from smoking so they would try to look at CHD separately from smoking

Answer 52

Comparability with respect to all other determinants of outcome Assuming groups are as similar as possible without that one factor/ exposure In order to compare groups, need to assume this The way that counterfactual theory becomes possible

Answer 53

Subtracting Frequencies (count) = A - B Ex: 65 surgeries in males and 27 surgeries in females - males had 38 more surgeries or females had 38 fewer surgeries (65- 27) Smaller than relative differences

Answer 54

Division of Frequencies (ratio) - = A / B - ex: 65 surgeries in males and 27 surgeries in females - males had 2.4 times the number of surgeries compared to females ( > 140% increase) Division of Proportions - ex: 65 / 70 surgeries in males (93%) and 27/ 59 surgeries in females (102% increase) - females had just 49.5% of proportion of surgeries compared to males - ratio of group proportions

Answer 55

Probability of outcome in an individual group based on exposure or non-exposure Proportion Helps us understand the impact of exposure on disease Used to see the association between exposure and outcome, the changes exposure can have, the impact/ relationship of outcome and exposure between 2 groups Also known as incidence risk - proportion

Answer 56

= A / (A + B) | Outcome = numerator because it is the new case that is occurring in the population

Answer 57

= C / (C + D) | If people are not exposed, why are they getting the disease/ outcome?

Answer 58

= B - A Risk difference of the outcome attributable to exposure difference between groups Also known as attributable risk Can attribute risk to difference in exposure

Answer 59

= ARR/ R unexposed | Need to ask what the baseline risk is - what would happen if I didn’t take the medicine?

Answer 60

= 1 / ARR - always round up to next whole number Number of patients that need to be treated in order to receive the stated benefit or harm - How many patients need to be treat vs harm in order for the effects to occur? To prevent harm, want NNT to be small and NNG to be large

Answer 61

Also known as relative risk or incidence Ratio of risks from 2 different (unrelated) groups = risk of outcome in exposed / risk of outcome in unexposed If ratio = 1 - outcome is equally likely for both groups - numerator = denominator If ratio > 1 - outcome is more likely to occur in comparison group (numerator) - numerator > denominator If ratio < 1 - outcome is less likely to occur in comparison group (numerator) - numerator < denominator

Answer 62

= 1.0 - no difference/ increase/ decrease in risks, odds, hazard - n = d > 1.0 - increased ratio - + 1.01 - +1.99 = use decimal value as percent - this will never be considered ‘decreased’ - n > d > 2.0 - increased/ greater risk/ odds/ hazard - use phrase ‘x times greater’ - n > d < 1.0 - decreased ratio - 0.0001 to 0.99 = subtract from 1.0 and convert answer to percentage - this will never be considered ‘increased’ - n < d

Answer 63

1. Group comparison orientation - exposed vs non-exposed 2. Direction of words - increased vs decreased - above 1 vs below 1 3. Magnitude - 80% = 1.8 times vs 20% = 0.80 times

Answer 64

Visual representation of ratios Puts multiple ratios together Components - center line and 1.0 = equalness - 1:1 ratio - to the right or left of center line = either greater or lesser than 1

Answer 65

Frequency of an outcome occurring vs not occurring - Likelihood of event occurring / likelihood of event not occurring Ratio - comparing 2 different things

Answer 66

Ratio of the odds from 2 different groups = Odds of exposure in disease / Odds of exposure in non-diseased = AD / BC = (A / C) / (B / D)

Answer 67

Lack of Exchangeability (comparability) A 3rd variable that distorts a measure of association between exposure and outcome Alternative explanation of the association

Answer 68

Independently associated with exposure Independently associated with outcome Not directly in the causal- pathway linking exposure and outcome Shown in DAG - direct acyclic graph

Answer 69

Looking at exposure and outcome relationship while ignoring other factors - not looking at confounds Unadjusted association Calculation of odds ratio/ risk ratio

Answer 70

Outcome measure of association between exposure and outcome for each individual level of the 3rd variable Weighted average of all levels Authors must tell what variables are used in the adjusting

Answer 71

Calculate crude association Calculate adjusted association Compare crude vs adjusted measures = absolute difference of crude and adjusted measures / crude measure - if crude and adjusted estimates are different by 15%: confounding variable is present

Answer 72

Magnitude of association - strength of association - association more extreme or less extreme than crude association - becomes not as impactful because exaggerates the real measure of association Direction of Association - produces association in opposite direction

Answer 73

To get a more precise/ accurate estimate of the measure of association between exposure and outcome

Answer 74

During Study Design stage: - Randomization, restriction, matching Analysis of Data stage: - stratification, multivariate statistical analysis

Answer 75

Allocates an equal number of subjects with the known and unassessed confounders into each intervention group Strengths: - will be successful with large enough sample size - stratified randomization more precisely assures equalness Weaknesses: - sample size may not be large enough to control for all unknown/ unassessed confounders - process doesn’t guarantee successful, equal allocation between all intervention groups for all known and unknown confounders - only practical for intervention studies

Answer 76

Study participation is restricted to only subjects who do not fall within pre-specified categories of confounder Strengths: - straight forward, convenient, and inexpensive - doesn’t negatively impact internal validity Weaknesses: - sufficiently narrow restriction criteria may negatively impact ability to enroll subjects - reduced sample size - if restriction criteria is not narrow enough, it will allow introduction of residual confounding effects - eliminates researchers ability to evaluate varying levels of the factor being excluded - can negatively impact external validity

Answer 77

Study subjects selected in matched pairs related to the confounding variable, to equally distribute confounder among each study group Strengths: - intuitive, some feel it gives greater analytic efficiency Weaknesses: - difficult to accomplish, can be time consuming, and potentially expensive - doesn’t control for any confounders other than those matched on

Answer 78

Descriptive/ statistical analysis of data evaluating association between exposure and outcome within various strata within the confounding variable Strengths: - intuitive, straight forward, and enhances understanding of data Weaknesses: - impractical for simultaneous control of multiple confounders, esp those with multiple strata within each variable being controlled

Answer 79

Statistical analysis of data by mathematically factoring out the effects of the confounding variable Strengths: - can simultaneously control for multiple confounding variables - OR’s can be obtained and interpreted Weakness: - process requires individuals to clearly understand and interpret the data - can be time consuming

Answer 80

Also known as interaction A 3rd variable that modifies the magnitude of effect of a true association by varying it within different strata of a 3rd variable - modifies the effect across the strata If present, we must report the measures of association for each strata individually - do not want to control for/ adjust these Is present when the odds ratio changes substantially according to different strata of the effect modifying variable

Answer 81

Calculate crude measure of association between exposure and outcome - odds ratio, risk ratio Calculate strata specific measures of association between exposure and outcome for each strata of the 3rd variable - odds ratio, risk ratio Compare each of the strata specific measures of associations between each other - measure of association between the lowest and highest strata of the effect-modifying variable will be 15% different if effect modification is present

Answer 82

A precursor event, condition, or characteristic required for the occurrence of the disease or outcome Help us understand things better Not just one cause - usually multiple- component factors

Answer 83

Relationships between an exposure/ treatment and outcome/ disease 1. Artifactual associations 2. Non-causal associations 3. Causal associations

Answer 84

Arise from bias and or confounding Something generates false measure of association Makes us think there is a relationship but there isn’t

Answer 85

Occurs in 2 different ways 1. Disease may cause the exposure rather than exposure causing disease 2. Disease and exposure are both associated with a third factor (confounding) - can create mild distortion - there is still a relationship between disease and exposure

Answer 86

Exposure directly linked to outcome

Answer 87

Type of causal relationship Precursor event that is sufficient enough on its own to induce disease and does so every time. A set of minimal conditions/ events that inevitably produce disease - can still have multiple, required components Rare - except for genetic abnormalities

Answer 88

= Risk Factors Type of causal relationship A factor/ element that if present/ active increases the probability of a particular disease - Multiple, required components that collectively act to induce disease Some patients must be primed or susceptible to disease before component causes induce disease - usually involves age - more risk factors + more time = more likely to get disease

Answer 89

Type of Causal Relationship A cause precedes a disease and has the following relationship with it: - cause must be present for disease to occur but cause may be present without disease occurring Cause is not sufficient to induce disease by itself but is needed to make the diagnosis

Answer 90

Biological interaction of 2+ component- causes such that the combined measure of effect is greater than the sum of individual effects Factors work together; both

Answer 91

Biological - interaction of 2+ component- causes such that the measure of effect is greater if either is present Needs one or the other but not both Factors work in parallel; either Occurs if both risk factors are present but measure of association doesn’t change

Answer 92

Multiple risk factors working together to collectively become sufficient- causes Component- causes have correlations - collectively and with enough time present in patient

Answer 93

Asks “what do we need in order to make the jump from association to cause?” 1. Strength 2. Consistency - specificity 3. Temporality 4. Biologic Gradient 5. Plausibility - coherence, experiment, analogy The higher number of criteria met, when evaluating an association, the more likely it may be causal

Answer 94

Causal Inference Process | - an interpretive, application process

Answer 95

First category of Hill’s criteria The size of the measure of association The greater the association, the more convincing it is that the association might be causal - the larger the number, the more important it is Ignores the concept of changing exposure Dependent on disease and exposure and their relationship

Answer 96

Second category of Hill’s criteria Also known as reproducibility The repeated observations of an association in different populations under different circumstances in different studies May still obscure the truth - observational studies over long time can lead us astray - Menopausal Hormone Therapy - disproved via the Women’s Health Initiative Study

Answer 97

Third category of Hill’s criteria Reflects that the cause precedes the effect/ outcome in time Time- order: - Proximate causes = short term interval - distant causes = long term interval Want to start looking at closest - there could be delayed hypersensitivity - ex: drug side effect

Answer 98

A number of studies have shown higher lung cancer rates among former smokers during the first year after cessation compared to those who continue to smoke Inference: continuing to smoke must decrease the risk of lung cancer Actuality: substantial portion of those who voluntarily stop smoking at any given time do so because of early symptoms and signs of the already-existing but as yet undiagnosed illness

Answer 99

Fourth category of Hill’s criteria Presence of a gradient of risk associated with degree of exposure - dose response Looking at intensity - whatever relationship is with less exposure, as exposure increases, the risk is changed - wrt negative component cause: more of it should be bad Some demonstrate a threshold effect - no effect until a certain level of exposure is reached - ex: lead exposure and mental retardation

Answer 100

Fifth category of Hill’s criteria Presence of a biological feasibility to the association, which can be understood and explained (biologically, physiologically, medically) Want to answer the questions: “does it make sense? Can we explain it?”

Unit 1 - Definitions and Equations Flashcards

(128 cards)