Chapter 4 - Study Design Overview and Cross Sectional Studies Flashcards
What are the main categories that studies can be divided into?
Observational and Intervention
What can observational studies be divided into?
Descriptive or Analytical
What are the general aims of observational studies?
- Describing a disease in a population
- Studying the associations between the occurence of disease and possible causes
What are intervention studies typically?
Clinical trials that study the effect of new drug or treatment
They involve asking the question: Does removing the characteristic reduce the probability of developing the disease?
What is the aim of a descriptive study?
Aim is to describe the prevalence of a disease and how this varies over time from place to place or by characteristics of the individual (such as age, sex or occupational group)
What is an important aspect of descriptive studies?
Identification of the population denominator (either from census data or routine data sources)
What are descriptive studies usually based on?
Case series or case registers (vital statistics)
Why are descriptive studies useful?
- Suggest clues to the causes of disease
- Enable assessment of the burden (in economic and health terms) of disease in different communities
- Distributions and correlations may be studied between time, place and person
Are descriptive studies relevant to the study of causes in disease in populations or individuals?
Populations
What is the aim of analytical studies?
They examine associations between the presence of diseases in individuals and populations and potential causative factors
Can you infer causality in analytical studies?
No
What are three type of questions usually answered in analytic studies and what are their corresponding study designs?
- Have the disease - cross sectional studies
- Develop the disease- cohort disease
- Have a characteristic - case control studies
Difference of an analytic study from descriptive study
In analytic study:
Information on controls (those without disease) is as detailed as for cases (those with disease). It is then possible to investigate the reasons why certain individuals become sick within a population.
Definition of cross sectional studies
A cross sectional study (prevalence study or survey) focuses on everyone in a define population (or sample of pop) and aims to determine their disease and/or exposure status at THAT POINT IN TIME.
It may be descriptive (assessing burdens of disease or exposure in population)
It may attempt to explain the observed pattern of disease by examining its relationship with possible aetiologic factors.
Often cross sectional studies contains elements of both descriptive and analytical studies.
Advantages of cross sectional studies
- Continuous (quantitative) disease outcome can be handled rather than yes/no outcomes
- Case definitions independent of standard health systems can be used so all diseases can be recorded
- Disease prevalence measured (burden)
- Multiple causes of disease can be studied
- Multiple consequences of a given exposure can be studied