Observational studies – which typically account for around 15% of all studies per year – are a method of clinical research that help scientists answer a specific question, or form a hypothesis for further investigation.
This type of study is frequently used within healthcare as it offers a cost-effective and relatively quick way to assess specific conditions, risk factors, and outcomes. Observational studies can also be used when other research methods aren’t available or appropriate.
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What is an observational study?
As the name suggests, observational studies involve collecting data from people simply by observing them, or by using existing data to collect information, without influencing the outcome. Researchers observe groups of participants over a certain timeframe, but are careful not to manipulate the study in any way.
This type of research is typically used to answer a research question, or to study rare events retrospectively and determine likely causes. It is also useful for determining probable cause and effect relationships that can help create a hypothesis for testing in future controlled experiments.
Depending on the reason for the research, the participants being observed might be healthy, have a particular illness, or be more likely to develop a condition if it runs in the family. As well as being observed, they may be asked to meet with the research team.
Why are observational studies important?
Observational studies play an important role in clinical research as they give scientists the opportunity to analyze relationships that can’t be tested via other methods, such as randomized controlled trials (RCTs) or experimental studies.
They also complement RCTs by helping researchers formulate new hypotheses, establishing how many participants are needed for an RCT, proving the validity of RCTs in real-world settings, and evaluating which patients benefit the most from different interventions.
Why are observational studies important in healthcare?
Observational studies play a key role in healthcare by providing real-world evidence, such as how a specific therapy works for a particular group of patients. This information helps improve patient management and care.
These studies also enhance patient safety by identifying errors or adverse events in healthcare settings. They are often cost-effective and can be conducted relatively quickly without needing large groups of participants, making them a practical tool for healthcare research.
Types of observational studies
Scientists typically use one of three types of observational study for clinical research purposes, each with its own uses and advantages.
Case-control studies
Case-control observational studies compare a group of people with an existing condition (cases) with another, similar group of people who do not have the condition (controls). Researchers examine historical factors to identify whether the cases were more commonly exposed to any risk factors. If they were, the scientists might hypothesize that there’s a link between them.
Cohort studies
Cohort studies focus on ‘at risk’ individuals and separate them into subgroups based on whether they were exposed to the factor being studied or not. They are typically used to assess the prevalence of particular outcomes, such as negative effects of medical interventions or drugs.
Cohort studies can track multiple outcomes over various periods of time, comparing how many people are affected in a group exposed to a risk factor versus those who aren't. This helps researchers understand the impact of the risk factor.
Cross-sectional studies
Similarly to cohort studies, cross-sectional studies look at the relationship between exposures and outcomes of interest. However, they focus on a single point in time. For example, they can show how common certain diseases or conditions are within a group of people at that moment.
These studies are useful for getting a snapshot of health trends and identifying patterns, but they don't track changes over time.
Types of observation
Researchers use various types of techniques to gather data depending on the type of study they are undertaking.
Naturalistic observation
Naturalistic observation involves observing participants in real-world settings without influencing their behavior or intervening in the study. Researchers simply watch and record behaviors and interactions as they naturally occur. This approach helps to gather authentic and unaltered data about how individuals or groups behave in real-world settings, providing valuable insights into natural behaviors and interactions.
Participant observation
This type of observational study typically observes people in a real-life setting, but the researchers actively engage with the group or setting they are studying. This means the researchers not only observe but also take part in the activities and experiences of the participants. Participant observation can also take place in a laboratory setting if appropriate.
Systematic observation
Systematic observation involves one or more researchers observing particular behaviors or events as they happen, and gathering and recording quantitative data. It might involve a strict observational schedule along with detailed coding to accurately measure how often something occurs.
Covert observation
Covert observations rely on participants being unaware that they're being observed, which can prevent in-group bias, and stop the ‘observer effect’ from happening, where individuals change how they behave because they know they're being watched. However, participants are unable to give their informed consent, which makes this approach ethically complicated and discouraged.
Quantitative observation
Quantitative observations involve gathering data that can be counted or measured. They usually involve gathering numerical data that can be reported as a quantitative value. Researchers use structured methods, such as surveys or experiments, to gather measurable information, which is then analyzed using statistical techniques.
Qualitative observation
Conversely, rather than gathering numerical data, qualitative observation relies on the observer’s five senses – reporting what they see, hear, feel, taste, or smell. Researchers use methods such as interviews, focus groups, or detailed observations to gather in-depth and descriptive information.
Case study
Case study observational research involves the detailed analysis of a single person, group, or event, enabling researchers to understand complex topics impacted by various influences. The research can then be extended to other groups or people if required.
Case studies are useful for exploring complex issues, generating hypotheses, and providing insights into unique or rare conditions. However, because they focus on one case, their findings may not always be generalizable to a broader population.
Archival research
Also known as secondary content analysis, archival research involves analyzing data that has already been gathered, or documents and media that might reveal certain practices, attitudes, or preferences. Sources might include the internet, archives, and libraries.
How are participants selected for observational studies?
Participants selected for observational studies can be based on several factors, including:
- the source population they come from, which might be a particular community, hospital, or doctors’ practice.
- whether they have been exposed to the factor being studied, such as smoking.
- their risk of developing the outcome, as people not at risk might be excluded.
- whether they belong to an exposed or unexposed group as they need to be selected from the same source (unless it’s a case-control study).
- whether they have given consent for data from their medical records to be used.
Benefits of observational studies
Due to their very nature, observational studies are usually straightforward as they simply involve observing behaviors or analyzing existing data. They allow researchers to study participants that can’t be randomized safely, ethically, or efficiently.
In cases when the study aims to discover the possible cause of a condition, comparing patients with and without the condition can be an effective way to find out.
They’re also a low-cost and efficient alternative to controlled trials, with their findings often paving the way for larger, more detailed clinical trials in the future.
Disadvantages of observational research
Observational study designs have their limitations and are open to more dispute than controlled trials. They usually have a higher potential for both observer bias, and undetected confounding variables or omitted variables, which can impact the reliability of the results.
They might also present inconclusive results that aren’t generalizable. Plus, they’re unable to determine the safety or efficacy of the medical intervention or treatment being studied.
The difference between observational studies and other types of research studies
Observational studies are significantly different from other types of research, mainly because no variables are manipulated, and they are completed within real-world rather than controlled settings.
Observational vs experimental studies
Observational and experimental studies differ in how they approach research. An observational study doesn’t influence the behaviors or responses of the participants, and instead, gathers information that occurs naturally. On the other hand, an experimental study involves manipulating one or more variables, often in a controlled environment.
Additionally, the participants in experimental studies are usually randomized, while this isn’t the case in an observational study.
Observational vs randomized controlled trials (RCTs)
RCTs take place under tightly controlled conditions that involve very specific populations that are randomly applied to groups. Observational studies, meanwhile, happen within real-world settings and the participants are not randomized.
Observational studies are also relatively cost-effective, efficient and quick to undertake by comparison. However, randomization in clinical trials is the best way to control confounding variables and prevent bias.
Examples of observational studies
Many groundbreaking observational studies have been undertaken that have provided invaluable insights into various behaviors and conditions.
Jane Goodall’s research into animal behavior
One famous observational study is Jane Goodall’s discovery that chimpanzees use tools, which was a landmark moment in anthropology and psychology. Goodall would simply enter the research subjects’ natural habitat and note down what she observed – and those behaviors included the chimpanzees using twigs to dig for termites.
Mary Ainsworth’s research into infant attachment
Mary Ainsworth visited Uganda in 1954 to study mother and infant attachment and bonding – making this one of the first studies in this area. Ainsworth observed 26 families over the space of two years, and the resulting academic papers became the basis for her ‘Strange Situations’ test which was conducted in a laboratory setting and involved observations with a two-way mirror.
She concluded that there were three types of attachment: secure attachment, insecure avoidant attachment, and insecure ambivalent attachment – with disorganized attachment added by researchers in later years.
Conclusion
Observational studies provide a cost-effective, efficient, and relatively straightforward way to make important scientific discoveries – particularly when it comes to determining the risk factors and outcomes of particular conditions.
Although observational studies have their limitations, this type of study can pave the way to creating and testing innovative new treatments and interventions – highlighting that all clinical research is important and has its unique applications and advantages.