Chapt 6 &7 Epidemiolgy

Ecologic Study

A study used based on the aggregate data collected at the broup level

Weakness of Ecologic Study

Ecologic studies are more susceptible to confounders as exposures and outcomes are not measured at the individual level

Ecologic Fallacy

the characterists at the population level are true for individuals at the individual level

Cross Sectional Study

Uses aggregate data to compare exposures to outcomes at one specific moment in time (at the same time)

Strengths of a Cross Sectional Study

1. Control over a population study

2. Several associations between variables at the same time

3. Data captured from same diseased individuals

4. Prevalence (All) data type

Cross Sectional Weakness

1. No time relationship btwn exposure & outcome

2. Follow-up loss & bias

3. Not feasible with rare exposures

4. Does not yield incidence or relative risk

A Cross Sectional Survey

Conducted over a short period w/ no follow up period

Time trend Study

Compares variation outcome data to exposure data across a specific time period in the same community

Solely Descriptive

Explores differences in risk factors or health outcomes between populations at the same time or within a given population

Types of Ecologic Studies

• Cross Sectional

• Time-Trend

• Solely Descriptive

A goal of a case control study is to

compare individuals with the specific disease with individuals without the diease, examine differences in exposures and identify risk factors

case control study design

study is retrospective, researchers look back to gather data on exposures

*can cause recall bias, faster study