University:
American Career College
Course:
NURS115 | Intermediate Medical
Academic year:

2020
Views:

125

Pages:

12
Author:

Gracie Bullock

PRINCIPLE OF EPIDEMIOLOGY COHORT STUDIES Observational studies 2 Cohort studies Cohort Study Population Design Cohort Study Steps  Hypothesis definition  Selection of exposed and unexposed  Follow-up and outcome measurement  Analysis & interpretation Selection of the Exposed Population • Sample of the general population:  • A group that is easy to identify:  • Geographically area, special age groups, birth cohorts Nurses health study Special population (often occupational epidemiology):  Rare and special exposure Selection of the Comparison Population • Internal Control Group – Exposed and non-exposed in the same Study population (Framingham study, Nurses health study) • • External Control Group – • Minimise the differences between exposed and nonexposed Chosen in another group, another cohort (Occupational epidemiology: Asbestosis vs. cotton workers) The General Population You follow the participants to:     The occurrence of outcome Loss to Follow-up Define the outcome Define “loss” Types of Cohort studies • Prospective Cohort Studies – – – • Time consuming, expensive More valid information on exposure Measurements on potential confounders Historical Cohort Studies – – – – Quick, cheap Appropriate to examine outcome with long latency periods Difficult to obtain information of exposure Risk of confounding Cohort studies Exposure Disease Yes No Total Yes a b n1 a +b No c d c +d n2 b+d N a+c Comparing cohort and case-control Case control cohort Study group Diseased/ healthy Exposed/ unexposed temporality Hard to establish Easy to establish multiple exposures outcomes time short Long cost inexpensive Expensive Best when D rare E frequent E rare D frequent Problems Control selection Exposure information Unexposed selection change over time