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EHS 3310 > Environmental Epidemiology (15) > Flashcards

Environmental Epidemiology (15) Flashcards

1
Q

epidemiology:

A

the study of the distribution and determinants of health and diseases, morbidity, injuries, disability, and mortality in populations

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2
Q

**environmental epidemiology:

A

the study of diseases and health conditions (occurring in a population) that are linked to environmental factors

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3
Q

environmental epidemiology exposures are usually voluntary/involuntary

A

involuntary

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4
Q

issues surrounding this field include exposure-response gradients, discovery of how occupational exposures cause harmful effects, identification of vulnerable workers, and input into programs for the prevention of occupationally related diseases

A

occupational health

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5
Q

**wrote the chimney sweeps story: environmental (occupational) cause for cancer; population medicine… a population of chimney sweeps

A

Sir Percival Pott (1775)

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6
Q

**“father of field epidemiology,” cholera in London

A

John Snow (1854)

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7
Q

Environmental epidemiology studies a population in relation to…

A

morbidity and mortality.

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8
Q

Epidemiology: generally observational or clinical?

A

observational

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9
Q

4 study designs used frequently in environmental epidemiology:

A

cross-sectional, ecologic, case-control, cohort

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10
Q

Prevalence:

A

refers to the number of existing cases of a disease, health condition, or deaths in a population at some designated time

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11
Q

Point prevalence (definition):

A

refers to all cases of a disease, health condition, or deaths that exist at a particular point in time relative to a specific population from which the cases are derived

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12
Q

Point prevalence (formula):

A

(number of persons ill) / (total number in the group) at a point in time

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13
Q

Case fatality rate (definition):

A

provides a measure of the lethality of a disease

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14
Q

Case fatality rate (formula):

A

CFR (%): [(number of deaths due to disease X) / (number of cases of disease X)] • 100 during a time period

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15
Q

The two types of study designs:

A

Experimental, Observational

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16
Q

Type of study design that uses randomization of human subjects into treatment and control groups (clinical trials) – VERY impractical and SELDOM used within epidemiology

A

Experimental

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17
Q

“Natural experiments” where the investigator acts as a disinterested observer; data is collected on past and present exposures and illness in a study population

A

Observational

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18
Q

Two classes of observational studies:

A

Descriptive, Analytical

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19
Q

Descriptive Study:

A

type of observational study in which disease/exposure trends and patterns are described and characterized, which generates a hypothesis for further study; depiction of the occurrence of disease in populations according to classification by person, place, and time variables

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20
Q

Analytical Study:

A

type of observational study in which illness and exposure variables are considered to understand whether there is a significant association between disease and exposures (explores causality and utilizes hypothesis testing)

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21
Q

Which type of observational study is hypothesis generating, and which is hypothesis testing?

A

Descriptive – hypothesis generating, Analytical – hypothesis testing

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22
Q

The two primary functions of descriptive studies:

A
  1. to assess variations in the occurrence of disease in populations
  2. to aid in the development of etiologic hypothesis
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23
Q

case series:

A

observational; hypothesis generating; collecting and analyzing information on a disease or condition that subjects have in common (ex. land applications of biosolids and health effects)

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24
Q

cross sectional:

A

observational; hypothesis generating; examines the distributions of disease prevalence and exposure in a defined population at a particular point in time; limited value for investigating rare disease or diseases of short duration, but can be useful for persistent diseases and is low-cost

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25
Q

ecologic studies:

A

observational; hypothesis generating; correlate group or population level measures of disease incidence with group or population measures of exposure (ex. # of WNV disease in each Ohio county and # WNV + mosquitoes… is there a correlation?)

26
Q

Limitations of ecologic studies:

A

nothing is known an an individual or local level about the disease incidence, for instance, there may not be a high number of human cases because the local health department implemented a very strong control and prevention program

27
Q

case control studies:

A

observational; hypothesis testing; subjects are chosen based upon disease status (cases have the disease being studied; controls do not)

28
Q

case control studies are more efficient for rare/common diseases, good for diseases that develop quickly/take a long time to develop, can study only one potential exposure/multiple exposures

A

rare, long time to develop, more than one potential exposure

29
Q

Odds ratio:

A

a measure of association for case-control studies; = AD/BC (OR > 1 suggests positive association between exposure and disease or health outcome)

30
Q

Cohort studies:

A

observational; hypothesis testing; subjects are defined based upon exposure status and followed over time to determine the incidence of the health outcome

31
Q

Timing of cohort study: prospective vs. retrospective

A

Prospective: follows exposure to outcomes forward in time (e.g. test blood lead levels over time, then assess intelligence) (gold standard, but expensive and seldom done in environmental epi)
Retrospective: exposure and outcome already occurred at time study begins (e.g. breast implant surgery patients having disorders)

32
Q

Relative risk (definition and equation):

A

the ratio of the incidence of a disease or health outcome in an exposed group to the incidence rate of the disease or condition in a non-exposed group
RR = [A/(A+B)] / [C/(C+D)]
(RR>1 - risk is greater in exposed vs nonexposed., = 1 no risk, <1 indicates possible protective effect)

33
Q

Parts of epidemiological triangle:

A

host, agent, environment

34
Q

Criteria for causality:

A
  1. strength of association
  2. consistency of association
  3. temporality** (ALWAYS needs to be satisfied)
  4. coherence
  5. specificity
  6. biological gradient
  7. biological plausibility
35
Q

Bias:

A

a skew in the availability of data, such that observations of a certain kind may be more likely to be reported and consequently used in research

36
Q

The healthy worker effect:

A

employed workers have lower mortality rates than general populations, which could introduce selection bias into occupational mortality studies

37
Q

Confounding:

A

the existence of other factors that contribute to the outcome of the study; arises from complex correlations of exposures in real life

38
Q

Effect of bias:

A

moves the measured relative risk away from the true value

39
Q

Selection bias:

A

arises from methods used to obtain study participants from the base population

40
Q

Information bias (also, misclassification/observation/measurement bias):

A

involves misclassification of either health outcome or exposure status; the major issue in environmental epidemiology studies

41
Q

Classic example of recall bias:

A

mothers of infants with birth defects are more apt to remember information about potential exposures than mothers with healthy infants

42
Q

Limitations of epidemiologic studies (4):

A
  1. long latency periods
  2. low incidence and prevalence
  3. difficulties in exposure assessment
  4. nonspecific effects
43
Q

**What is the major issue in environmental epidemiology studies?

A

exposure misclassification! (there is an error in the classification of an exposure; i.e. an exposed subject is classified as non-exposed or vice versa)

44
Q

Characteristics of environmental epidemiology (3):

A
  1. deals with nondisease effects
  2. involves numerous variables
  3. tends to be community-specific
45
Q

Weaknesses of environmental epidemiology (3):

A
  1. sample size is insufficient
  2. important variables “uncontrolled”
  3. exposure estimation invalid
46
Q

Strengths of environmental epidemiology (3):

A
  1. engages the real world
  2. unique perspective on disease/health
  3. basis for action despite ignorance of mechanism
47
Q

Ecological fallacy/bias (limitation fo ecologic study):

A

researcher cannot assume that an association/correlation found at a population level will represent an association at the individual level

48
Q

Benefits of ecologic studies (3):

A
  1. inexpensive
  2. can use existing data sets
  3. studies on individuals do not reveal complex relationships of the transmission of infectious diseases in the environment and how ecological factors effect that transmission
49
Q

Case control studies are more/less costly and more/less efficient that cohort studies.

A

less, more

50
Q

Limitations of case-control studies:

A
  1. can only test one (or two) diseases at a time
  2. not good for rare exposures
  3. exposure data may not be accurate (biased) because it is collected back in time (retrospectively) – recall bias, exposure misclassification, selection bias
  4. difficult to determine if exposure came before disease
  5. confidentiality must be protected
51
Q

Selection of controls in case control studies:

A
  • must be free of the disease at the time of selection
  • should meet the “would criterion” (would be case if got disease
  • up to 4:1 ratio of controls:cases
52
Q

Cohort studies:

  1. are efficient for common/rare exposures
  2. are efficient for common/rare outcomes
  3. generally more/less accurate than case control studies
  4. can/cannot evaluate multiple effects of an exposure
  5. Efficient/inefficient for diseases with long latent periods
  6. Less/more vulnerable to prospective bias
  7. Less/more vulnerable to retrospective bias
  8. can/cannot measure disease incidence
  9. temporal relationships between exposure and disease are/are not clear
  10. T/F expensive and time-consuming
A
  1. rare
  2. common
  3. more accurate
  4. can
  5. efficient
  6. less
  7. more
  8. can
  9. are
  10. True
53
Q

**Circa 400 B.C., Hippocrates wrote…

A

…“On Airs, Waters, and Places,” which was about how environmental and host factors such as behaviors might influence the development of disease

54
Q

**In 1662, John Graunt wrote a…

A

landmark publication based on Bills on Mortality, quantify patterns of birth, death, and disease occurrence, noting disparities across population groups

55
Q

**1800: William Farr…

A

modern vital statistics and surveillance

56
Q

**19th and 20th centuries-

A

epidemiological methods applied in investigation of disease occurrence of communicable nature

57
Q

**1930s and 1940s-

A

non-communicable diseases were also investigated for their risk-factors, i.e., Doll and Hill- linking lung cancer to smoking

58
Q

**1960s and early 1970s-

A

health workers applied epidemiologic methods to eradicate naturally occurring smallpox worldwide

59
Q

**1980s -

A

extended to the studies of injuries and violence

60
Q

**Contemporary epidemiology-

A

HIV/AIDS, SARS, MDRTB, Avian Flu, also, biologic warfares and bioterrorism

EHS 3310 (10 decks)

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