Exam 1 Flashcards
In Ghost map, what factor placed an individual in London at risk of getting Cholera?
Cool water at the pump so it was enticing, close proximity to the pump
What’s wrong with people recommending cures they believe to be effective based on their personal experience? What is the standard of evidence needed to deem a drug useful?
Bias, lack of evidence
Heresay is often the first step to start research.
Quantitative and qualitative in clinical settings. If the benefits outweigh the risks. If it is effective in clinical trials.
Correlation is not causation- explain two difference in the text of how this is true
Miasma theory: “miasma was present if there was a bad smell.
Lower altitude= people are more likely to get sick
The poor the person, the dirtier the house, more likely to get sick= not true because whitehead stopped in one of the dirtiest homes and found that no one had fallen ill with cholera
What about a city creates or intensifies an epidemic?
Dense urban areas, very little sanitation and food sources
Explain the contagion model. How did Snow become convinced of the truth of the contagion model. What question did he wrestle with and how did he resolve those questions?
the contagion theory is that there is an “agent” or particle which spreads to people causing the disease. Snow became convinced of this by the lodging house spreading to others as well as linking it to a common water source among towns. He wrestled with the question of why it would affect some people in the household but not everyone he was also trying to figure out how the water got infected In the first place.
How did a public health intervention actually lead to cholera’s lucky break? Can you think of any modern parallels in which public health intervention has actually made a problem worse?
The sewer systems that London had built to make the city “cleaner” ended up dumping cesspools into the river but Londoners were drinking the river water which led to cholera.
GMO’s, nutrition (fat free)
What was the miasma theory? why did so many intelligent individuals falsely hold to the miasma theory even though there was lot of evidence to disprove it? How did social prejudice blind people to the evidence against the miasma theory?
If the air stinks then that means that there is a disease present
Very instinctual, “if food smells good then eat it, if food smells bad then don’t eat it.”
Poor people stink more which means that there is more disease present.
What did John Snow determine was actually the cause of cholera epidemic and how did he “build the case” for how cholera was transmitted? What evidence did he use? What comparisons did he make? Describe the background of the problem, the methods used to gather data, the results of the investigation and the conclusion.
He discovered the actual cause of cholera to be the drinking water at Broad Street Pump. John Snow walked around to where major outbreaks occurred and found a common correlation being the water. He used Farr’s list to help. Looked for deviations from his hypothesis (Who died from cholera that didn’t live near Broadstreet) He was getting out into the community going door to door asking people about their illnesses.
Make a list of what John Snow did and didn’t know about cholera
He knew: ratios of survival, exemptions of people who didn’t drink water and convinced it was waterborne, if cholera was really coming from the poor there would be a greater discrepancy between the poor and rich contracting cholera
Didn’t know: How it originated in the pump, why not every household would be affected
What convinced Whitehead of Snow’s theory? What information did whitehead have that snow didn’t
Whitehead talked to people who fled areas and was able to track down baby Lewis. He was investigating the survivors.
Mom of baby Lewis admitted to throwing feces in the water
Tracked the kids getting water for the family
What is an index case? Who was it? Why was it important to find?
An index case is the first that begins the epidemic
Baby Lewis
The family had a unique pathway to the main pump
How did John Snow famously test the role of the water supply in causing cholera deaths in London? How else could the role of the water supply be tested?
The pump handle was removed from the broad street pump which led to a drastic reduction of cholera cases. The best results would come from intervention studies.
What conclusions can be drawn from figure 1.1 and how does this evidence strengthen the conclusion drawn by Doll and Hill based on their 1948 study?
It is a very linear relationship between number of cigarettes and lung cancer. This is strong evidence of a causal relationship.
What conclusions can be drawn from figure 1.2
The graph shows that smoking only causes excess mortality in the age ranges greater than 50
what factors need to be considered when interpreting geographical distribution of disease. How might researchers miss the distribution of disease in certain geographical regions and areas
distribution of the population
knowing whether the search for cases has been as intensive in the areas without cases as it has been in the areas with cases
epidemiology
the study of distribution and determinants of health-related states or events in specified populations, and the application of this study the prevention and control of health problems
Strength of Association
if measures of affect are large, association is likely to be causal
what is the strength of the association between the cause and the effect?
Consistency
similar results with different studies, different investigators, different methods and different populations
Specificity
Single factor - Single Disease
Lack of specificity does not mean lack of causality
temporality
Does the effect come after the cause
Biologic Gradient
Does increasing exposure increase the effect?
Plausibility
Observed association can be plausibly explained with existing knowledge
Does it fit what we would expect to happen with what we already know
Coherence
No plausible competing theories
Experiment
Evidence is based on randomized experiments
Analogy
the relationship is in line with other cause-effect relationships
This criterion uses previous evidence of an association between a similar exposure and disease outcome to strengthen the current argument for causation.
Which Bradford Hill Criterion will always hold true?
temporality
Exposure of interest always precedes outcomes by a period consistent with the proposed mechanism
what is the difference between necessary and sufficient
Necessary: Required for disease to occur
Sufficient: Set of factors working together, requires joint action of component causes, each component plays a necessary role
what is fundamental to getting the right prevalence and incidence
Population at risk
what are the three measures of disease frequency
Population at risk, Incidence, Prevalence
Population at risk
demographic, environmental and geographic factors that increase risk of exposure to a disease
Incidence
represents the rate of occurrence of new cases
total number of new cases/ total population at risk
prevalence
frequency of existing cases in a defined population at a given time
number of people with the disease/ number of people exposed to risk
cumulative incidence
Simpler measure of occurrence- measures the denominator only at the beginning of the study
case fatality
measures the proportion of cases with a specified disease who die within a specified time
prevalence is dependent on both incidence and disease duration, if prevalence is low
p= incidence x average duration of disease
Is prevalence a useful measure of frequency of type 2 diabetes in different populations? Why would researchers use prevalence rather than incidence?
Yes, because prevalence measures the amount of people that are currently diagnosed with this disease whereas incidence measures new cases. Since Diabetes isn’t curable only paintable incidence wouldn’t be a good measure.
Health Determinants
Underlying social, economic, cultural and environmental factors responsible for health and disease
Health Indicators
Variables measured directly to reflect the state of health of people in a community
What are the two different ways to compare disease occurrence
Absolute and Relative
What are the 3 sub categories of absolute comparison
Risk Difference: difference in rates of occurrence between exposed and unexposed groups in the population
Attributable Fraction: Proportion of all cases that can be attributed to a particular exposure
Population Attributable Risk: incidence of a disease in a population that is associated with an exposure to a risk factor
What are the 2 sub categories of relative comparison
Relative risk: the ratio of the risk of occurrence among exposed people to unexposed
Attributable risk: rate of disease in exposed individuals that can be attributed to the exposure
Sources of morbidity data
hospital admissions and discharge outpatient and primary healthcare consults specialist services (injury treatment) register of disease events
what measures are used to compare the frequency of disease in populations and what information do they provide?
Risk ratio: the ratio of the risk of the disease among exposed to the unexposed. Answers the question WHAT PROPORTION of cases of X would we expect to eliminate if we could Eliminate the exposure?
Risk difference: difference in rates of a disease or condition between exposed and unexposed groups in the population. Answers the question HOW MANY occurrences of X would we expect to eliminate if we could eliminate the exposure
what is the main reason for standardizing rates to a population with a standard age distribution? How does this allow us to compare populations with very different age distributions?
Age standardization ensures that differences in death rates are not due simply to differences in age distribution in the population, allows for the comparison of populations with different age structures.
Let’s say you want to know where the most cancer deaths per capita occur within a country. What would be the reason to use crude death rates and what would be the reason to use age-standardized rates? How would the two rates give you different information?
Crude rate tells you where the number of cases per capita is highest, but high crude rate could mean a larger population of old people. Age standardized rate tells us where the risk of cancer is highest. Without having age standardized rates for both countries, comparisons are impossible.
