CH. 6 public health
19. Explain syphilis: The cause agent, symptoms and treatment.
- spread by sexual contact - symptoms: Blindness Heart disease Dementia Paralysis Death
8. What is a common source of error in a large case-control study?
Error in reporting or recall (interview bias). Subjects do not remember their past exposure.
MAJOR THEMES
Even well-designed studies may produce erroneous findings. Clinical trials are considered to yield the most accurate results, and cohort studies the next most accurate. When conflicting results are found by different major studies, epidemiologists are challenged to understand what has led to these differences. This has been the case with two major trials on the health effects of hormone replacement therapy for post- menopausal women.
Tuskegee study
a notorious example of an unethical study, beginning in 1932, in which 400black men with syphilis were observed over time but not treated, to observe the course of untreated syphilis; the subjects were misled as to the nature of their participation.
Confounding variables
a possible source of error in epidemiologic studies; factors associated with an exposure that may independently affect the risk of developing the disease.
20. It was established RULES for the conduct of human experimentation. All institutions that receive federal funds MUST follow these rules. Explain each of them:
a) Every research subject must be informed of the purpose of a study and its risks and benefits b) Subjects must freely consent to participate c) Any such study must be approved by an institutional review board a committee that includes representatives of the community as well as other scientists d) They must agree that the study is: well designed its benefits outweigh its risks and subjects are truly given the opportunity for informed consent
7. What is a common source of error in a large cohort study?
Confounding variables, hard to recruit and screen for volunteers with the same background (age, diet, education, geograph, etc.)
Institutional review board
a committee, including scientists and representatives of the community, that must evaluate all proposed studies before they can be conducted; the committee must agree that the study is well designed, that its benefits outweighs its risks, and that subjects are truly given the opportunity for informed consent; required for all institutions that receive federal funds
Informed consen
a fundamental rule, established following the revelations about the Tuskegee study, for the conduct of human experimentation; research subjects may participate in a study only if they freely agree to participate after being informed of the purpose of a study and its risks and benefits.
16. Which of the following studies has given the most valid result?
a. Exposure to aspirin during a viral infection causes Reye's syndrome (odds ratio 42.7)
Bias
systematic error in the design or conduct of a study that leads to a false association
11. It is of vital importance that the data collected have 4 desirable characteristics. Which are they?
- reliable (consitency in the measurement process) - valid (truthfulness) - unbiased (no distortions) - culturally appropriated (people from different cultures are likely to possess different values, beliefs, traditions, and perceptions. These differences affect nearly all activities of individuals, including their health-relates behavior and responding to questions related to health)
2. There are 2 types of measurement error. Which are they?
- systematic error - random error
17. Have you heard of the Tuskegee Syphilis Study? Why was it unethical? What influence has it had on the conduct of clinical trials?
- the purpose was to observe the course of the disease in men (poor, black and uneducated men with syphilis) who were not to receive treatment even after 1940s after penicillin was discovered - unethical because they refused to treat them and let them die - racist study led many African - americans to mistreat medical field
MAJOR THEMES
. Because epidemiology studies humans, there are many limits to how research can be conducted and many pitfalls in interpreting the results. Limits are imposed by ethical considerations and because researchers cannot control the behavior of their subjects.
5. Define "measurement". What is the difference between quantitative and qualitative data?
An internal part of program planning and evalution. It is the process of assigning numbers or labels to objects, eents, or people according to a particular set of rules. It can be quantitative (numerical data) or qualitative (narrative data) measures.
1. What is the ultimate goal of many epidemiologic studies?
Determine the cause of disease by observation, formation of hypothesis and testing hypothesis.
MAJOR THEME
Drug companies are required by the FDA to conduct randomized controlled trials demonstrating the safety and effectiveness of all new drugs. Evidence has appeared over the past decade that companies use various strategies to bias research in favor of the drugs. Many drugs had harmful side effects that were missed in the companies' trials and, in some cases, were suppressed by the companies. Now, all such trials must be registered in advance in a public database.
MAJOR THEMES
Each type of epidemiologic study is subject to certain types of errors. Sources of error include random variation, especially likely in small studies, and various forms of bias and confounding.
MAJOR THEMES
Current studies on humans funded by the federal government must obey strict ethical rules including informed consent by the patients and review of the study design by institutional review boards.
14. Epidemiologic studies, no matter how well designed to avoid error, can not prove cause and effect. Epidemiologists usually speak of risk factors rather than cause. There are several factors that can be combined to make the cause-and-effect relationship almost certain. What are the factors that lend validity to results (proving cause & effect). Explain each of them.
1. large study population (a large number of subjects is more likely to yield a valid result than a small study) 2. strong association ( the stronger the association measured between exposure and disease, the more likely that there is a true cause and effect relationship) 3. dose-response relationship between exposure and risk of disease ( as evidence that supports exposure as a cause of the disease) 4. known biological explanation (epidemiologic evidence is more convincing if there is a known biological explanation for an association between an exposure and a disease ) 5. consistent results from several studies
13. In 1965 Austin Bradford Hill proposed a series of considerations to help assess evidence of causation. Which are they?
1. strength (larger association, more likely that it is causal) 2. consistency 3. specificity (causation is likely if a very specific population at a specific site and disease with no other likely explanation) 4. temporality (effect has to occur after the cause ( and if there is an expected delay between the cause and expected effect, then the effect must occur after that delay) 5. biological gradient (greater exposure should generally lead to greater incidence of the effect) 6. plausibility (if it makes sense) 7. coherence (coherence between epidemiological and laboratory finding increases the likelihood of an effect) 8. experiment (occasionally it is possible to appeal to experimental evidence) 9. analogy (the effect of similar factors may be considered)
9. What is a common source of error in a small epidemiologic study?
Chance (random error, random variation). If a group being studied is too small, a cause-and-effect relationship is likely to be missed or a spurious relationship will show up by chance alone.
10. Explain possible sources of error in an epidemiologic study:
CHANCE(RANDOM ERROR, RANDOM VARIATION) most likely to occur when sample is small (random error) - Bias (systematic error) Selection bias (intention to participate) Particular problem in choosing subjects for case-control Reporting bias or recall bias Common problem is case-control studies Occurs if the study group and the control group systemically report differently even if the exposure was the same - Biology (biologic mechanism of interest), and - Confounding variables Factors that are associated with the exposue and that may independently affect the risk of developing the disease Referred to as bias from co-occurance or mixing of effects of extraneous factors
21. Epidemiologic studies are complicated, with many opportunities to make honest errors in interpreting them... but when millions of dollars are at stake, which is the case with clinical trials of new prescription drugs, it is increasingly obvious that conflicts of interest often affect reported results. Explain the 2007 Food and Drug Administration Revitalization Act.
It requires all clinical trials must now be registered in advance in a public database sponsored by the national library of medicine
12. Explain why data must be culturally appropriated?
Have to be careful because of lack of knowledge of culture. We must listen and observe to try to sit in their shoes. No bias
4. Which error is unpredictable? Why? When does it cause? How can we reduce it from occurring?
Random error is unpredictable and typically fluctuates during the reading of a measurement apparatus or in the experimenter's interpretation of the instrumental reading. They can be estimated by comparing multiple measurements, and reduced by averaging multiple measurements and increasing the sample size
6. What is a common source of error in a large randomized controlled trial (intervention study)?
Subjects may not follow prescribed behavior throughout study period
3. Which error is also known as "Bias"? Explain this type of error.
Systemic error: not determined by chance, not affected by sample size. Is introduced by an inaccurary in the system. It is predictable and typically constant
Selection bias
an error due to systematic differences in characteristics between those who are selected for a study and those who are not
18. Which of the following statements about ethics and epidemiology is true?
d. It is unethical for insurance companies to deny bone marrow transplants, an expensive experimental procedure, to women with advanced breast cancer.
The contradiction between the Nurses' Health Study and the Women's Health Initiative as to the benefits and risks of hormone replacement therapy was caused by:
d. Random variation
Recall bias
error that occurs when there is a differential level of accuracy in the information provided by compared groups; in a cohort study, it occurs when exposed subjects are more or less likely than unexposed subjects to recall and report subsequent disease; in case-control studies, it occurs when cases are more or less likely than controls to recall and report prior exposures
