Cross-Sectional Studies Flashcards
Definition of Cross-Sectional Studies
- Observational studies that capture health/disease and exposure status at the same time.
AKA Prevalence study
Why are cross-sectional studies so named?
Because information gathered represents what is occurring at a point in time or time-frame across a large population.
Acquired without regard to exposure or disease/outcome status
Who is selected for a cross-sectional study?
Entire population or a subset
What does a cross-sectional study focus on?
- focuses simultaneously on disease & population characteristics, including exposures, health status,…
- Seeks associations
- Generates and tests hypotheses
- by repetition in different time periods
What are the two cross-sectional approaches?
- Collect data on each member of the population
- Take a sample of the population & draw inferences to the remainder
What is a probability sample?
Every element in the population has a known probability of being included in sample
What are some examples of probability sampling schemes?
- Simple Random sampling
- Systematic Random sampling
- Stratified Simple Random sampling
- Stratified Disproportionate Random sampling
- Multi-Stage Random sampling
- Cluster Multi-Stage Random sampling
Simple Random Sampling
- Assign random sampling, then take randomly-selected number to get desired sample size
- Assign random numbers, then sequentially-list numbers and take desired sample size from top of numbers
Systemic Random Sampling
- Assign random numbers, then randomly sort the numbers, select the 1st or last number and then every Nth number from there
Stratified Simple Random Sampling
Stratify by desired characteristic, then use Simple Random sampling to select desired sample size
Stratified Disproportionate Random Sampling
- disproportionately utilizes stratified sample when baseline population is not at the desired proportional percentage to the referent population
- stratified sample ‘weighted’ to return sample population back to baseline pop
Multistage Random Sampling
Uses simple random sampling at multiple staged towards patient selection
Cluster Multistage Random Sampling
Same as multistage random sampling but all elements clustered together or selected for inclusion
Non-probability sampling schemes
- Quasis-systematic or Convenience samples
Quasi-Systematic or Convenience samples
Decide on what fraction of population is to be samples and how they will be sampled.
Eg. All persons with last name A-H
What are the two common broad approaches to collection of study data/information?
- questionnaires/surveys
- physical assessments
What are the advantages of cross-sectional studies?
- Quicker & easier for the researcher when using data already collected
- Less expensive for researcher than any form of prospective study
- Can be analyzed like a Case-Control or Cohort study
- Useful for estimating prevalence rates
- Useful for answering research questions about a myriad of exposure and diseases
What are the disadvantages for Cross-Sectional Studies?
- Prevalent cases may represent survivors
- Difficult to generate incidence rates
- Problems in determining temporal relationship of presumed cause & effect
National Health and Nutrition Examination Survey (NHANES)
Assesses the health & nutritional status of adults & children
- Combines interviews & physical examples
- Interviews include demographic, socioeconomic, dietary, & health-related questions
- Examination component consists of medical, dental, physiological measurements and lab tests
National Health Interview Survey (NHIS)
- Principle source of information on health of the civilian, non-institutionalized population
- Data are collected through a personal household interview
- Consists of a core set of questions that remain largely unchanged & a set of supplements used to respond to public health data need as they arise
Ambulatory Health Care Data (NAMCS)
- Provides reliable information about the provision and use of ambulatory medical care services in the US.
- Based on a sample of visits to non-federal, office-based, physicians primarily engaged in direct patient care
National Hospital Care Survey (NHCS)
- A combined national survey designed to describe national patterns of healthcare delivery in non-federal hospital-based settings
Behavioral Risk Factor Surveillance System
- State-based system of telephone surveys that collects info on health risk behaviors, preventative health practices, and health care access primarily related to chronic disease and injury
