Longitudinal Study

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Longitudinal Study Longitudinal study
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This article covers what longitudinal study is, what are its types, the different ways of collecting data for a longitudinal study, as well as its advantages and disadvantages.

What is a longitudinal study?

Longitudinal surveys, on the other hand, involves studying variables for a long period of time and observing the changes in them from time to time. Here, the data is collected from the respondents at the beginning of the study, and then the researcher collects data at different time intervals until the end of the study. Longitudinal surveys are more popularly used in medicinal science to understand and evaluate the effects of medicines, or vaccines, in the long-run on participants. Because longitudinal surveys take place for several years, researchers can establish the sequence of events that may affect the variable under study.

Longitudinal studies involve the use of research surveys in order to collect qualitative or quantitative data. In a longitudinal study, the creator of the survey does not intervene with the participants of the survey. Instead, they distribute the questionnaires over time in order to observe changes in the participants, their behaviour, or attitudes. Most medical studies tend to be longitudinal where the researchers collect data and observe the same participants over several years.

What are the types of longitudinal studies?

Longitudinal studies tend to be versatile, replicable, and they can account for both quantitative and qualitative data. There are three major types of longitudinal studies that can be the basis for future research:

  • Panel Study: A panel study is a type of longitudinal study that examines the same sample over a period of time. Here, the study is conducted at specific intervals for an extended period of time. Most panel studies tend to use quantitative analysis, though, they may sometimes be used to collect qualitative data as well for a qualitative analysis.
  • Cohort Study: In a cohort study, researchers study samples of different cohorts. Cohort studies are most popular in medical research and some even consider clinical trials to be a kind of cohort study. However, in cohort studies, researchers simply observe participants without interfering with the study, while in clinical trials participants do undergo certain tests. 
  • Trend Studies/Analysis: Trend Studies are most common in mass media research. Here, researchers sample different groups of people at different times from the same population and analyse the changes within the groups over a period of time. Example; seeing the shift in people’s attitudes during presidential elections.

How do you collect your own data for a Longitudinal Study?

If you plan to collect data for your longitudinal study, the way you go about collecting it will be determined whether you are doing a retrospective or a prospective study.

In a retrospective study, the data is collected on events that have already happened. Whereas, in a prospective study, one can choose a group of participants, follow them over time and collect data in real time. In general, retrospective studies are less time consuming and cost-effective as compared to prospective studies. However, they are also more prone to error in measurement as compared to prospective study.

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What is the Difference Between Cross-sectional and longitudinal studies?

Longitudinal study

Although both cross-sectional and longitudinal research methods are quantitative in nature, there are several differences amongst them. In a cross-sectional study, researchers collect data of a variable at a specific point in time while in a longitudinal study, the data is collected at different times. In longitudinal studies, variables tend to change over time as well. 

Researchers use cross-sectional research to find commonalities between different variables. They use longitudinal studies in order to dissect the findings of the cross-sectional study further. Let’s look at the differences between the two in detail:

Longitudinal studies

Cross-sectional studies

Longitudinal studies take a longer time to be completed, ranging from years to even decades sometimes. 

Cross-sectional studies tend to be less time-consuming and quick to administer. 

Here, the researcher observes participants at different periods in times

Here, the researcher conducts the study over a predetermined specific period of time.

Cause-effect relationship is provided by longitudinal studies.

Cause-effect relationships are not provided by Cross-sectional studies.

Here, only one variable is observed and studied in detail.

Here, different variables are observed at a single point in time.

Longitudinal studies are more expensive and thus, not very accessible to companies and researchers. 

Cross-sectional studies are cost-effective and thus a popular means of study for companies and researchers. 

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What are the advantages and disadvantages of conducting longitudinal surveys?

This section covers the advantages and disadvantages of conducting longitudinal studies:

Advantages of longitudinal studies”

  • Since longitudinal studies allow researchers to follow the participants or subjects in real time, the data collected is highly valuable, enriching, insightful, and valid. This also gives promising and valid results for the study.
  • Longitudinal studies also offer long-term unique and rich data. This is different from cross-sectional studies that only collect short-term data. Longitudinal studies thus permit us to discover long-term relationships between variables.
  • Longitudinal studies also help researchers to uncover and analyse trends from the collected data in real time whether it is a medical study, psychological or a sociological study. 
  • Longitudinal studies allow researchers to observe the variables in the same sample over a period of time. Thus, any changes in the variable can be correctly attributed to the individual.
  • Longitudinal study surveys are flexible as well since it is a long-term study.  
  • Longitudinal studies also eliminate the risk of bias because the researchers are observing and collecting the data in real time.


    Disadvantages of longitudinal studies
  • The main disadvantage of longitudinal studies is that it is unpredictable. Since researchers plan to study the same number of people over time, the drop out rate of participants can also be high and the previously collected data will be useless.
  • Longitudinal studies are time-consuming and costly. It requires a large amount of commitment as well as resources on the part of the researcher.
  • Longitudinal studies also take time to uncover relationships between variables. Moreover any unpredictable event in the natural world can lead to changes in the variables instead of individual factors and hamper the study.
  • Longitudinal studies require large amounts of samples for the study to yield meaningful patterns and insights.

The advantages show us the enormous value of longitudinal studies have to offer, and the disadvantages tell us how to properly plan and execute longitudinal studies to avoid errors and potential biases.

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Types of Market Research that use a longitudinal study

Longitudinal studies help us compare various business and branding aspects in market research which in turn help us in creating and deploying relevant surveys. Some of the examples of surveys that are used by market researchers when conducting a longitudinal study are:

  • Market research surveys help researchers to identify market trends as well brand development strategies to implement. These surveys help businesses and organisations to learn what their customers like and dislike, and make decisions in accordance to that. This study can be conducted over time in order to assess the trends of the market repeatedly and market conditions tend to be dynamic in nature.
  • Longitudinal studies can also employ product feedback surveys. These surveys are usually used when the business launches a new product or service and wishes to know how it is doing in the market. Here, they collect feedback from customers about the particular product over a long period of time and then gain insights from it.
  • Longitudinal studies also assess customer satisfaction. Customer satisfaction surveys help businesses to analyse how satisfied or dissatisfied the customers are with a brand. Longitudinal studies help researchers collect data from new as well old and regular customers. The data collected helps them in gaining insights into areas that need improvements and the practices that are working well for the company.
  • Longitudinal study surveys can also help researchers assess employee engagement. The company analyses the behaviours of the employees in the long run to get a deeper understanding of the company’s culture. These surveys help researchers to understand if employees feel comfortable working with their colleagues and the level of motivation they have towards work.

What are the examples of longitudinal studies?

Example 1: Smoking and Cancer

If researchers want to understand how smoking affects the development of cancer in later stages of life, they would choose participants who are different from other observable variables but similar in one: smoking. In this case, researchers would observe the participants who started smoking from adolescence into later adulthood and examine the changes in their body that are caused due to smoking. They can see how smoking has influenced the immunity of participants, their reaction to stress, and other variables relevant to the researcher. Over time, researchers can also observe the effects of quitting smoking if some participants decide to quit smoking later in their life. This will help researchers understand the interaction between health and smoking in more detail.

Example 2: Violent video games and aggression

Suppose a researcher wants to understand if playing violent games is linked with violent behaviours. They could collect data from a large amount of participants for the study. In order to reduce the influence of habits, researchers can choose individuals who already play video games a lot. With parental consent, researchers can observe the age groups of 13 to 19 for the study. The researchers will have to first establish a baseline of the aggression in the participants at the onset of the study for later comparison. The researchers can ask the participants to keep track of time they spend playing video games. The study can last from months to years. During this period, the researchers can correlate the amount of time participants play the video games, the violent content of the game, and the aggressive behaviours of the participants and thus establish a link between aggression and violent video games.

Create and analyze a longitudinal study survey

You can conduct your own longitudinal study by creating an insightful survey with the help of Voxco! You can use our survey templates or build your own survey from scratch, you can use Voxco for building your marketing strategies or medical studies, we are here to help you through it all!

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