What is a Longitudinal Study? — Definition and Explanation

A longitudinal survey can pay off with actionable insights when you have the time to engage in a long-term research project. But before you can start planning your next survey, you need to be familiar with the longitudinal study definition: an observational study that employs continuous or repeated measures to follow particular individuals and observe the same set of variables over a prolonged period.

This might seem intimidating, but keep in mind that the longitudinal study definition in psychology and all other disciplines do not include experimentation. It’s strictly observational and analytical. As long as you have the time to record the observations at repeated intervals, you can conduct a longitudinal study. That’s where surveys can help; they can capture feedback directly from multiple participants at once.

In this article, we take a closer look at the defining characteristics of longitudinal studies, review the pros of this type of research, and discuss some longitudinal study examples. Let’s start by digging into what this kind of study is and is not.

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What is a longitudinal study?

Longitudinal studies often use surveys to collect data that is either qualitative or quantitative. Additionally, in a longitudinal study, a survey creator does not interfere with survey participants. Instead, the survey creator distributes questionnaires over time to observe changes in participants, behaviors, or attitudes. Many medical studies are longitudinal; researchers note and collect data from the same subjects over what can be many years. 

Characteristics of a longitudinal study

Using the same individuals or samples in the longitudinal study is to observe any measurable change over time. It ensures that you can account for the same variables of interest in the duration of your research.

A longitudinal study is not restricted to the field of science or medicine. It also impacts business. With a longitudinal survey, researchers can measure and compare various business and branding initiatives. Some of the classic examples of longitudinal surveys include:

Many medical studies are longitudinal; here, a set of a sample or similar individuals form a group. Researchers observe and study the group over the years. The purpose of using the same individuals or samples in a longitudinal study to see them and review any measurable changes over a period.

Types of surveys that use a longitudinal study

With a longitudinal study, one can measure and compare various business and branding aspects by deploying surveys. Some of the classic examples of surveys that researchers can use for longitudinal studies are:

  • Market trends and brand awareness: Use a market research survey and marketing survey to identify market trends and develop brand awareness. Through these surveys, businesses or organizations can learn what customers want and what they will discard. This study can be carried over time to assess market trends repeatedly, as they are volatile and tend to keep changing.
  • Product feedback: If a business or brand launches a new product and wants to know how it is faring with consumers, product feedback surveys are a great option. Collect feedback from customers about the product over an extended time. Once you’ve collected the data, it’s time to put that feedback into practice and improve your offerings.
  • Customer satisfaction: Customer satisfaction surveys help an organization get to know the level of satisfaction or dissatisfaction among its customers. A longitudinal survey can gain feedback from new and repeat customers for as long as you’d like to collect it, so it’s useful whether you’re starting a business or hoping to make some improvements to an established brand.
  • Employee engagement: When you want to check the “pulse” of your workplace, gather feedback with an employee engagement survey. Find out whether employees feel comfortable collaborating with colleagues and gauge their level of motivation at work. When you check in regularly over time with a longitudinal survey, you’ll get a big-picture perspective of your company culture.

Now that you know how researchers use longitudinal studies across several disciplines let’s identify the three types of studies you might conduct with your survey.

Types of longitudinal studies

Longitudinal studies are versatile, repeatable, and able to account for quantitative and qualitative data. Consider the three major types of longitudinal studies for future research:

  • Panel study: A panel study involves a sample of people from a more significant population and is conducted at specified intervals for a more extended period. One of the panel study’s essential features is that researchers collect data from the same sample at different points in time. Most panel studies are designed for quantitative analysis, though they may also be used to collect qualitative data and analysis.
  • Cohort Study: A cohort study samples a cohort (a group of people who typically experience the same event at a given point in time). Medical researchers tend to conduct cohort studies. Some might consider clinical trials similar to cohort studies. However, in cohort studies, researchers merely observe participants without intervention, unlike clinical trials in which participants undergo tests.
  • Retrospective study: A retrospective study uses already existing data, collected during previously conducted research with similar methodology and variables. While doing a retrospective study, the researcher uses an administrative database, pre-existing medical records, or one-to-one interviews.

Longitudinal studies vs. cross-sectional studies

Longitudinal studies are often confused with cross-sectional studies. Unlike longitudinal studies, where the research variables can change during a study, a cross-sectional study observes a single instance with all variables remaining the same throughout the study. A longitudinal study may follow up on a cross-sectional study to investigate the relationship between the variables more thoroughly.

The difference between the studies is the timeline and variable. In a cross-sectional study, researchers observe the same constant variable and carry out research only once. A researcher finds different variables over time in a longitudinal study and collects data based on those studies. For instance, business strategists might gather social, lifestyle, and financial information from their target audience. Then they study the effect of these factors, both separately and in combination, and build an action plan related to the business’ offerings from these findings.

 Advantages of conducting a longitudinal study

As we’ve demonstrated, a longitudinal study is useful in science, medicine, and many other fields. There are many reasons why a researcher might want to conduct a longitudinal study. One of the essential reasons is, longitudinal studies give unique insights that many other types of research fail. Take a look at the advantages of conducting a longitudinal study:

Benefits of a longitudinal study

  • A longitudinal study can identify and relate to events. You can reveal chronology between events like long-term and short-term changes in variables, making this ideal for medical studies.
  • Similarly, because longitudinal research is carried out over a long period, it helps identify and establish a particular sequence of events.
  • The longitudinal analysis provides meaningful insights that might not be possible with other research types like cross-sectional and similar studies.
  • A longitudinal study allows researchers to trace development over a timeline instead of drawing conclusions based on a “snapshot” of data.

Longitudinal study examples

For many researchers and strategists, the advantages of longitudinal research outweigh the disadvantages. Consider the examples included in this section and decide for yourself.

Longitudinal study example 1: Identical twins

Consider a study conducted to understand the similarities or differences between identical twins who are brought up together versus identical twins who were not. The study observes several variables, but the constant is that the participants all have an identical twin.

In this case, researchers would want to observe these participants from childhood to adulthood understand how growing up in different environments influences traits, habits, and personality. Over many years, researchers can see both sets of twins as they experience life without intervention. Because the participants share the same genes, it is assumed that any differences are due to environmental factors, but only attentive study can conclude.

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Longitudinal study example 2: Violence and video games

In this second example, a researcher is studying whether there is a link between violence and video game usage. They collect a large sample of participants for the study. To reduce the amount of interference with their natural habits, these individuals come from a population that already plays video games. Here the age group is restricted to teenagers (13-19 years old).

The researcher records how prone to violence participants in the sample are at the onset. It creates a baseline for later comparisons. Now the researcher will give a log to each participant to keep track of how much and how frequently they play and how much time they spend playing video games. This study can go on for months or years. During this time, the researcher can compare video game-playing behaviors with violent tendencies. Thus, investigating whether there is a link between violence and video games.

Conducting a longitudinal study with surveys is straightforward and applicable to almost any discipline. Browse our collection for 350+ free templates and research questionnaires and start building your longitudinal survey with QuestionPro today.