Prospective Study Vs. Retrospective Study: What’s The Difference?

There are many different types of studies that researchers use in order to draw conclusions about the world around us. There’s a lot of jargon, terminology, and overlap in the names and words used, making it difficult to know which kind of study is which.

Two major study archetypes are prospective studies and retrospective studies. Both of these are most often used in medical research, especially in diseases.

A prospective study is a study that looks forward, as in a group, usually called a cohort, is selected and observed for a time to see if they contract any illnesses. For example, more people who make regular use of tanning beds contract melanoma than the control group.

In a retrospective study, it’s the other way around. Researchers would interview a group of people with melanoma on how often they used tanning beds. From there, they would conclude whether or not tanning beds up your risk of skin cancer.

Key Takeaways:

What Is a Prospective Study?

A prospective study is a type of study that looks forward. Prospective studies are most often used to research illnesses and track the likelihood that a particular group of people will contract an illness as compared to the control group. Cancer is a major research topic, as are other diseases that appear later in life, such as type 2 diabetes.

• Prospective means “relating to or effective in the future.” Which is why a prospective study looks forward. It studies subjects in the present and future, seeing how they change over time.

• Prospective studies are almost always cohort studies. A cohort study is a type of study that selects a group of people due to a commonality. This can be as broad as being born around the same time or as narrow as engaging in the same hobby or behavior, like vaping.

  Many of these studies look at risk factors. For instance, does consuming more sugar make you more likely to get type 2 diabetes later in life?

  The researchers could then select a group of people who have high sugar consumption and a group with low sugar consumption and observe them over time, comparing how many of each cohort are diagnosed with type 2 diabetes.

• The studies are longitudinal in nature. As these studies look to the future, they tend to be longitudinal. That means that they take place over the years – even decades – with researchers checking in every so often to see how the participants have changed over time.

  This type of study is inherently expensive, as it requires a great deal of time, personnel, and keeping in touch with the participants over a long period of time.

• There are pros and cons to this type of study. As with all things, there are good things and bad things about this study model.

  • Pros

    • There’s a lower chance of bias.

    • Greater degree of control over data collection.

    • Allows for tracking over time.

    • Can look into multiple conditions at once.

    • More direct cause and effect determinations.

  • Cons

    • Longitudinal studies are very expensive.

    • Relies on participant transparency.

    • Rare diseases can be hard to study this way.

    • Requires a large pool of subjects to be effective.

• Overall, proactive studies are the preferred study type. Due to the longer-term nature of the studies, they’re preferred. This is mainly for two reasons:

  • First reason. Due to the subjects being selected early, it’s harder for bias to affect the study. This can be biased in terms of the participants misremembering or misrepresenting their past or the bias of the researchers gravitating towards certain people for their study.

  • Second reason. It’s easier to draw a cause-and-effect relationship than with a retrospective study. The researchers may be looking for a particular illness, but they aren’t going to seek out specific people who already have it – and they get to see what leads up to the illness manifesting.

What Is Retrospective Study?

A retrospective study is a study that looks at the past. For instance, if the researchers are looking to see if high sugar ingestion raises the risk of type 2 diabetes, they would interview a group of people who have the illness and ask them about their sugar consumption. This can give researchers a strong idea of the correlation between behaviors and illnesses.

• Retrospective means “based on memory.” A retrospective study starts with the condition that the subject has and looks into their past with the intention of explaining their present condition.

• Retrospective studies tend to be short. As this type of study is based almost entirely on interviews, they don’t tend to be long-term. It’s largely just a matter of finding individuals with the disease the study focuses on and gathering enough of them that are willing to participate.

  Of course, as with most studies, researchers do their best to get a representative sample. This can vary exactly on what they’re studying, but most modern studies do their best to include people of different races, genders, ethnicities, and geographic locations – unless they’re focusing on a specific population.

• They’re almost always cohort studies. By their nature, retrospective studies are usually cohort studies. They don’t always include a control group, as there are particular traits that researchers look for.

• There are pros and cons of retrospective studies. As with all types of studies, there are positives and negatives when it comes to retrospective studies.

  • Pros.

    • They’re much less expensive and require fewer resources.

    • There’s less of a time commitment from the participants, so it’s easier to get people to agree to it.

    • The results can be gathered much more quickly.

  • Cons.

    • It’s prone to bias.

    • The nature of the study makes finding a comparison group extremely difficult.

    • It can be hard to get together enough data to form a strong conclusion.

• Overall, retrospective studies are considered less reliable. While retrospective studies have their uses and advantages, they’re considered less accurate and reliable overall. Researchers are reluctant to draw conclusions as to causation from retrospective studies.

  There is also the fact that memory is faulty. Participants may overreport or underreport usage of whatever the researchers are asking them about. Depending on the questions and nature of the interview, the researchers can also end up pushing participants to tell them what they expect to hear, even if it’s not deliberate, which can skew the results.

Author

Di Doherty

Di has been a writer for more than half her life. Most of her writing so far has been fiction, and she’s gotten short stories published in online magazines Kzine and Silver Blade, as well as a flash fiction piece in the Bookends review. Di graduated from Mary Baldwin College (now University) with a degree in Psychology and Sociology.