Environmental Epidemiology Quiz - 9-30-18

Cohort Study

a group of people has followed over a period of time to see what happens to them and information about risk factors is collected we can then compare the occurrence of an outcome like disease in those who are exposed to a particular risk factor to those who are not exposed to that risk factor the main measurement used in cohort studies is called the relative risk a relative risk is the ratio between the risk of disease in the exposed group compared to the risk of disease in the unexposed group a relative risk of greater than one means that the exposure is associated with an increased risk of the disease if it is 1 it indicates that the risk is the same and if its less than 1 it indicates that the risk is lower Advantages - time sequences can be determined, collection of outcome/risk factor, sub analysts Disadvantages - cost, not good for rare diseases, ensuring people who started study

Case Series

describe the characteristics of a group of individuals with the same disease or the same exposure the aim is to understand the demographics, clinical presentation, prognosis, or other characteristics of people who have same disease or describe something unusual like pneumonia in mean leading to the recognition of HIV

Interventional Study

done on a group of people and the outcome studied examples of interventions can be giving a medicine a vaccine or health advice the outcome can be things like a change in disease status or change in behavior a randomized controlled study Advantages: good evidence of causality, randomization ensures that both groups have an equal chance of receiving the intervention and that they have similar characteristics Disadvantages: expensive many participants not always possible

Study

A scientific process of answering questions using data

Explain how overfishing is an example of tragedy of the commons

Each individual fisherman is motivated to take as many fish as he can for himself, meanwhile any decline in fish reproduction is shared by the entire village A fisherman will conclude that it's in his best interest to take an extra fish or two or three, unfortunately this is the same conclusion reached by the other fisherman Optimizing for the self in the short term isn't optimal for anyone in the long term

What is Tragedy of the Common?

Garrett Hardin revived the concept to describe what happens when many individuals all share a limited resource like grazing land, fishing area, living space, even clean air He argued these situations pit short-term self-interest against the common good and end badly for everyone resulting in overgrazing, overfishing, overpopulation, pollution, etc. The key feature of a tragedy of the commons is that it provides an opportunity for an individual to benefit him or herself while spreading out any negative effects across the larger population

Case control Study

Starts off with cases (people with a disease), uses comparison group (controls) both groups asked about their previous exposures to risk factors. For risk factors, the odds of being exposed as a case is compared to the odds of being exposed if they were a control this is called an odds ration an odds ratio of more than one means that people with the disease are more likely to have been exposed to that risk factor the people without the disease this suggests that it could be a possible cause of the disease an odds ratio of less than one suggests that its a protective factor and one suggest no association case control studies are commonly used in food borne outbreak investigations

More examples of tragedy of the commons

The overuse of antibiotics has led to short term gains in livestock production and in treating common illnesses It's also resulted in the evolution of antibiotic resistant bacteria which threatens the entire population A coal fired power plant produces cheap electricity for its customers and profits for its owners, these help in the short term, but pollution from coal and mining is spread across the entire atmosphere and sticks around for thousands of years Littering, water shortages, deforestation, traffic jams, the purchase of bottled water Humans form social contacts, make communal agreements, we elect governments, and we pass laws, all this to save our collective selves from our own individual impulses Humans have shown we can solve these problems if we remember Hardin's lesson When the tragedy of the commons applies, what's all of us is good for each of us

Cross-Sectional Study (Prevalence Studies)

takes a selected population and measures health information at a given point in time giving a snapshot of their health, it usually involved asking participants a series of questions using a questionnaire health surveys that collect information about people i a population is an example usually measure how many people have a disease a particular point in time relatively inexpensive and easy to conduct, info collected at single point in time so cannot be used to determine whether a particular exposure causes a disease or not

Ecological Study

type of study where measurements like disease rates and information about exposures are made on a group of people of any size results from these studies apply to a group and not individuals also useful for generating questions and highlighting issues that can lend themselves to future studies