Quiz 1 Flashcards
It is possible that Alzheimer’s disease has not been increasing in the U.S. since 1980, but rather diagnosis has improved.
If medical providers have become better at determining that a person has Alzheimer’s disease, then it will appear that the number of cases of the disease has increased even though there has been no true increase. In other words, if 10% of people with Alzheimer’s used to not be diagnosed because their presentation with the disease was unusual, but a diagnostic test becomes available that identifies this 10% as having Alzheimer’s, there is no true increase, just more people who end up diagnosed.
Epidemiology has played a role in which of the following (select all that apply):
Epidemiology has played a role in the following: people not being able to smoke in airplanes, needle exchange programs for injection drug users, and the calorie counts on the menu at restaurants in New York City (NYC). Epidemiologic studies have demonstrated that there is an association between second hand smoke and various diseases. These observations led to restricting smoking on airplanes so that other passengers were not exposed to second hand smoke. Epidemiologic studies have shown associations between needle sharing and HIV and hepatitis risk. As a result, needle exchange programs were established to mitigate this risk. The observed association between obesity and a variety of health outcomes prompted public health officials to implement interventions to help individuals make healthier food choices. One of these interventions, motivated by the knowledge of obesity as a risk factor for adverse health outcomes, was to provide calorie counts on restaurant menus.
Which of the following are potential explanations for an observed association (relationship) between an exposure and health outcome (select all that apply)?
All choices are correct: 1) We can never rule out chance. We may be able to say that an association is very unlikely to be due to chance, but it can never be completely ruled out. 2) There is likely to always be error in the measurement of an exposure. If the error is different between those who do and do not have the disease, a spurious association could be observed. 3) Similarly, there can be error in determining if someone has had the health outcome and if that error is different between those who are exposed and unexposed, a spurious association could be observed. 4) Finally, if the exposure does in fact cause the disease, it would definitely be an explanation for the findings. In epidemiology, we generally try to determine whether there are other likely explanations.
How many of Hill’s criteria MUST be met in order to establish a cause and effect relationship?
The correct answer is 1-2. Temporality absolutely must be met, and consistency (replication of findings) is also very important. Temporality and consistency do not always indicate a causal association, but at a bare minimum, we need to establish temporality (and some would argue also consistency) to even consider an association as potentially being causal. Note that for many associations, even those of true cause and effect relationships, not all of Hill’s criteria will be fulfilled. For example, we may not always see a dose response relationship because it is possible that there is a specific level of an exposure that is uniquely associated with adverse health outcomes.
It is correct for a physician to tell a patient who smokes that they will eventually develop lung cancer.
False is the correct answer. Although smoking is strongly associated with risk of lung cancer, it is neither a necessary nor sufficient cause for lung cancer. Thus, it would be incorrect for a physician to tell a patient this.
Component causes in a series of causal pies must occur in all of the pies
False is the correct answer. There are almost always multiple pathways to disease and for that reason different causal pies will have different components. A necessary cause would occur in all of the pies.
Exposure to the measles virus is… (select all that apply)
Exposure to the measles virus is a necessary and component cause, but not a sufficient cause, of measles. Not everyone who is exposed to measles will develop the disease and thus it is not sufficient to just be exposed. To develop measles, a person must be exposed to the virus; therefore it is a necessary cause. Exposure to the virus will be a component cause in all causal pies that lead to developing measles.
Which of Hill’s causal criteria must be established to further consider whether a cause and effect relationship exists?
Temporality must be established. This means that the exposure occurs before the outcome. If the exposure does not come first, it can not cause the outcome.
Select all of the true statements (select all that apply)
It is true that a relationship between an exposure and disease outcome does not imply causality. Alternative explanations for a relationship include chance, bias, confounding, and reverse causation. The other two statements are NOT true for the following reasons:
1) Replication of associations should be observed. Any study may be poorly conducted, so we cannot rely on only one study to establish causality.
2) We do not usually know all of the component causes in a pathway that leads to disease. Even though we know that smoking causes lung cancer, we do not know all of the components in the causal pie(s). There are likely multiple pathways with overlapping and unique component causes.
Obesity may lead to arthritis through chronic inflammation and excess weight bearing on the joints. This is an example of
This example provides the biologic mechanism (plausibility) that may explain the association. Coherence is met when laboratory and epidemiologic findings support each other. This is often not met as animal or in vitro models may not mimic humans well. Strength of the association describes the magnitude of the association. Temporality refers to being sure that the exposure came before the disease. Specificity is when the observed association is very specific to a given population.
