Observational child study is an important research method in which a researcher observes behavior in a systematic manner without influencing or interfering with the behavior. Observational studies draw inferences about the effect of an “exposure” or intervention, when the intervention is not specifically assigned by the researcher conducting the study. Observational child study methods are often used where there are ethical concerns in using an experimental design, such as exposure to cigarette smoking.
Observational child studies can illuminate real world exposure and provide important community-level data that can help inform clinical practice. While they cannot provide statements of fact about an intervention’s effectiveness or safety, observational child studies do present associations that can infer risks and benefits.
Observational child studies are often a first step towards experimental research, such as a randomized control trial (RCT). They give an idea about the incidence, prevalence, and prognosis of the disease that is studied, and this information is necessary for proper planning of the RCT.
In an observational study, the frequency of an outcome—or an exposure, depending on the study design—is measured, estimated, or described. Risks, rates, prevalence, and odds are common measures of the frequency of an outcome. These can be compared between groups and describe the association between exposure and outcome, providing the basis for the study’s conclusions.
Observational child studies typically fall into the following categories:
- Cohort (a group of people with one or more characteristics in common)
- Case–control (two groups with different outcomes are observed on the basis of some causal attribute)
- Longitudinal (follows a cohort of patients over time)
- Cross-sectional (looks at population data at one point in time)
- Ecological (observes at least one variable at a group level)
Cohort studies are usually either prospective or retrospective. In prospective studies, investigators enroll a cohort of patients, collect baseline data and then observe to see if outcomes of interest develop over time. In retrospective studies, investigators note outcomes of interest occurring and go back in time to identify a cohort of people at a point in time before they developed outcomes of interest and then look for exposure status. In clinical effectiveness research, this often involves review of electronic medical records. Because this type of data was not collected to answer specific research questions, investigators often have to adjust analyses for confounding factors that could be distorting the association of exposure to a specific risk and outcome.