Cross sectional study

An “observational” design that surveys exposures and disease status at a single point in time (a cross-section of the population)

1. STUDY DESIGNS

2. Types of epidemiological studies
•Types of studiesAlternative nameUnit of study
•OBSERVATIONAL STUDIES
–Descriptive studies
–Analytical studies
•Ecological Correlation Populations
•Cross-sectional Prevalence Individuals
•Case-control Case-reference Individuals
•Cohort Follow-up Individuals
•EXPERIMENTAL STUDIES(Intervention Studies)
–Randomized control trialsClinical Trials Patients
–Field trials Healthy People
–Community trial Community studies Communities

3. Difference between Descriptive and Analytical Epidemiology
DescriptiveEpidemiology Analytical Epidemiology
Only one group studies At least two groups are studied for
comparison
At thestart of study there is no
explicit hypothesis regarding cause
effect relationship
At the start of the studythere is definite
hypothesis regarding an exposure
possibly causing an outcome.
The study ends in development of
possible hypothesis regarding cause
and effect relationship but does not
confirmor reject such hypothesis
At the end of the study it confirms or
rejects the hypothesiswith which it
started

4. Cross-sectional studies
An “observational” design that surveys
exposures and disease status at a single point
in time (a cross-section of the population)
Time
Study only exists at this point in time

5. Reasons for doing a cross-sectional study
•To assess the burden of disease in a
population and to assess the need for
health services.
•To compare the prevalence of disease in
different populations.
•To examine trends in disease prevalence
or severity over time.

6. Cross-sectional Studies: characteristics
•Exposure and disease outcomes are determined
simultaneously
•Provides a snap shot view and hence measures
prevalence, not incidence of disease; Example:
community surveys
•Know the existence of disease but not the duration
•Often used to study conditions that are relatively
frequent with long duration of expression (nonfatal,
chronic conditions)
•Not suitable for studying rare or highly fatal diseases or
a disease with short duration of expression
•Examining effects on physiologic variables (e.g. Liver
enzyme levels, blood pressure, lung function)

7. Where can we do a cross sectional study
•Any setting or location
–Community
–Schools
–Worksite
–Hospitals