Environmental Epi Flashcards
Why do we think about env epi in relatively clean environments?
Low exposure, low relative risks but big populations = large disease burden (large # of cases)
What is prevalence?
Proportion of a population who have a specific characteristic in a given time period
Includes new and existing cases of disease
(ALL # of ppl w disease/total # in the population)
What is incidence?
Occurrence of new cases of disease in a population over a specified period of time (# of new cases/population at risk)
What are the strongest levels of the hierarchy of evidence?
Meta-analysis, systematic reviews, and randomized controlled trials (least biased)
What are the weakest levels of the hierarchy of evidence?
Animal studies & expert opinions (most biased)
Observational vs. experimental studies
Retrospective & prospective cohort studies vs. cross sectional studies vs. case control studies
Retrospective and prospective cohort studies strengths & weaknesses
Cross sectional studies strengths & weaknesses
Exposure prevalence examined in relation to disease prevalence at a single point in time
Strengths: can explore multiple exposures and outcomes; cheap
Weakness: issue of temporality (what came first, outcome or exposure)
Case control studies strengths & weaknesses
Identify cases first –> then select controls
Cases & controls arise from the same source population
Strength: good for rare diseases
What types of studies are useful for rare outcomes?
Case control studies!
What types of studies are NOT useful for rare outcomes?
