Longitudinal studies are a form of observational research that is used to collect data. When this type of study is performed, a set of data is collected from each subject over a defined period. The same subjects are used for the research, which means the study can sometimes last for months, if not years.
It is the type of research that is most commonly performed when seeking out information in medical, sociological, or psychological arenas.
Here are the top advantages and disadvantages of longitudinal studies to consider when designing a research study.
Top Advantages of Longitudinal Studies
1. Longitudinal studies make it easier to find long-term patterns.
Many research studies focus on short-term data alone. That means long-term data may offer patterns or information that cannot be collected. A longitudinal study would be able to collect that long-term data and locate patterns within it that can benefit the field being researched. This occurs because changes can be tracked over time as the same subjects are being used, allowing cause-and-effect relationships to be found.
2. They offer high validity levels through the collected data.
Because longitudinal studies are a long-term research project, there must be extensive policies and procedures in place from the very beginning of the project. These policies and procedures then dictate the direction of the study, requiring researchers to follow their outline. Because every data collection effort follows this establish protocol, longitudinal studies have high levels of validity because there is a certainty to the authenticity of the research. People can have confidence in the conclusions which are generated.
3. It uses observational methods for data collection.
Most longitudinal studies utilize observational data collection methods because of the long-term nature and design of the research. That makes the data much easier to collect when compared to other study formats. It also provides consistent data that can be applied across all developed metrics. Researches can then use this information to exclude differences or outliers in the data, increasing the overall accuracy of the research while excluding their own personal basis.
4. The format limits the number of mistakes that can be made.
Researchers may wish to draw their own conclusions from the data being collected, but the format of longitudinal studies prevents this from happening. That means from the data collection process to the conclusions that are published, the information being presented has a limited number of mistakes contained within it. That allows the data to be used to create needed changes within the researched field immediately, so that the rest of society can benefit from the conclusions.
5. It offers unique and authentic data.
Because longitudinal studies go directly to the source of information for data, what is collected is often authentic and unique. The principles of data collection allow for long-term relationships to be discovered within the data while short-term benefits can still be collected. It essentially offers the best of both worlds to researchers. Using the results from short-term data, researchers can pursue long-term data that may not have been considered when the study was first implemented.
6. There is more flexibility to be found within longitudinal studies.
Longitudinal studies can be designed to track a single data point. They can also be designed to track multiple metrics simultaneously. Researchers can pivot within the study if they find interesting or unique patterns in the data being collected. Data relationships can be pursued to determine if there is something meaningful within that information. At any time, a shift in focus is permitted if an interesting data point is discovered, which allows for the results and conclusions to be more complete when compared to other study formats and styles.
7. Data collection occurs in real-time.
Longitudinal studies happen in real-time, which means the data being collected is reflective of “now.” That makes it possible for researchers to expand questions or follow tangents based on the responses they receive from each individual. It creates more engagement, which builds a relationship between the subject and the researcher, and that can eventually lead to new insights that might have been held back otherwise.
8. It provides for multiple forms of data collection.
Human memory is a fickle beast. Two people can witness the same event and remember it in very different ways. This occurs because everyone has a unique perspective and their own experiences that affect their memory. For that reason, longitudinal studies offer multiple methods of data collection to ensure the accuracy of what is being collected. Video or audio recordings, diaries, journals, blogs – they can all contribute to the database of information that researchers collect, and then mine, to find conclusions that can be reached.
9. Longitudinal studies make an effort not to manipulate the environment.
This is the advantage of the observational approach that is used with this type of study. Instead of manipulating the environment to produce data, researchers simply collect the data that they can detect with their 5 senses. Asking questions may seem like world manipulation to some. What interviews provide is a way to access personalized information. As long as the researcher is proceeding based on what they observe, the manipulation effect is not present within the researcher.
10. It can be used to pursue developmental trends.
Longitudinal research is often used to determine if developmental trends have any future benefit. It is especially important when considering practical application fields like family medicine to determine better methodologies that can be applied to the general population. Researchers can also pursue trends that they observe on their own to see if there is any correlation between the subjects that would explain the information that they are seeing.
11. They can be used to establish a specific sequence of events.
One person who lives to the age of 100 can be an outlier in any community. Their combination of genetics, healthy living, and optimism, unique to them, can help them live long and happy lives. In a small community, having several people reach the age of 100 is no longer an outlier. There is the potential that there is something present within their environment that is encouraging longer life. Longitudinal studies make it possible to establish a specific sequence of events that would lead to such an outcome, offering the opportunity for that sequence to be duplicated elsewhere.
12. It corrects for the cohort effect.
Whenever there is a large group of people coming together for research purposes, you’re going to have a wide variety of individualized time components. These range from their date of birth, to their current age at the time of the study, to their overall net worth. The long-term nature of this type of study helps to correct any effects that might develop because of these differences, which reduces the individuality of the data that is collected.
Top Disadvantages of Longitudinal Studies
1. The format allows one person to influence the outcome of the study.
Longitudinal studies rely on the expertise, creativity, and honesty of individual researchers for authentic conclusions. That reliance on the individual makes it possible for the data to be corrupted or conclusions to be inaccurate. It does not need to be a purposeful manipulation of the data for the outcomes to be falsified. Misinterpreting data can be just as damaging as purposely misleading the collection of the data and the results would be difficult, at first, to be proven invalid.
2. It offers direct costs that are much higher than other research styles.
Larger sample sizes are required for longitudinal research than in other styles. This requirement is in place because more data is necessary in long-term studies to determine if there are relationships or patterns within the data. That means the direct costs of performing a longitudinal study are typically higher when compared to other research methods. More people must be contacted. More data must be examined. More time must be dedicated to the project. Other research formats do not face these challenges.
3. Long-term studies often see sample sizes change over time.
Larger sample sizes are required for a longitudinal study because of the nature of life. People eventually grow old and die. There may be accidents or natural disasters that occur during the data collection period for the study as well. That means some data may need to be excluded from the research to avoid providing false results and it may be difficult to locate the data that must be removed.
4. It can be difficult to locate willing participants.
Would you want to be tracked over the next 20 years of your life about something? There are three groups of people that researchers encounter when creating a longitudinal study. One group are enthusiastic and willing to help in whatever way they can. One group despises the idea of being contacted by researchers on a regular basis for a long time. The final group doesn’t really care and may not offer accurate data to researchers because of their apathy. Researchers look for enthusiastic participants for authentic data and those folks aren’t always easy to find.
5. Longitudinal research relies heavily on the expertise of each researcher.
Data collection in longitudinal research occurs in real-time, but that means it relies on the skills of the researcher to collect. The average researcher didn’t go to school for journalism, so their ability to recognize follow-up questions or focus on specific data points can be limited. The quality of the data that is collected relies on the quality of the expertise that the researcher brings to the project. That means the quality of the data can also vary if multiple researchers are collecting data.
6. It can have questions of data accuracy.
With a longitudinal study, it only requires one inaccurate data point to throw the entire validity of the study into question. That inaccurate data point can even invalidate years of research and it doesn’t have to be a purposeful collection to cause problems. Researchers are human, just like the rest of us. They have a personal bias toward certain subjects or certain data points that influence how they work, whether they realize it or now. It is not uncommon for researchers to draw conclusions about the data they are collecting before they’ve even collected the information.
7. Time is always an issue with a longitudinal study.
Researchers that begin a longitudinal study may not see the results that their study is able to generate. Some studies take several years to complete. One study, reported on by the Harvard Gazette, discusses a longitudinal study that will be 80 years old in 2018. Scientists began tracking the health of 268 Harvard sophomores in 1938 and as of 2017, 19 of them were still alive. The information collected from this study is important, but it has taken nearly a century for the results to be conclusive. As more data is collected, more time and resources must be utilized to go through the data and look for relationships as well.
8. Study participants may not offer authentic information.
Longitudinal studies involve the same participants over a long period of time. What happens to them can affect the data that is collected. It can also influence how future data is collected. All of this is based on a working assumption that the individual involved is being honest and forthright with the researcher. Some people may stop participating altogether. Unless there are policies and procedures in place that can help to prevent these outcomes, the validity of the study could be questioned before all the data is even collected.
9. Funding is a major challenge for longitudinal studies.
The costs of a longitudinal study don’t need to be prohibitive, but there are factors and influences that can make it difficult to justify the expense. Outside of the actual research cost, many studies of this type must budget for incentives or rewards to encourage subjects to continue their participation. Then, since participants are essentially compensated for providing data, researchers must ensure the information is valid because there will always be critics that question its validity. Some see the compensation of participants as a form of bribery.
10. Inaccuracies are common when analyzing data that is collected by this type of study.
Longitudinal studies often seen inaccuracies during the analysis of the data that is collected. These inaccuracies often arise when hypothesis testing is applied to the collected data, much like it would be for other types of research, such as a cross-sectional study. When this occurs with a longitudinal study, the available data is often under-utilized, which increases the chances of a statistical error occurring.
11. The variable being studied may disappear over time.
Even with the best planning process enacted, policies and procedures cannot stop the fact that a studied variable may disappear from the population group being studied. Should such an event occur, the time and money invested into the research study would be wasted because no valid conclusions could be drawn from the collected data.
The advantages and disadvantages of longitudinal studies direct us toward the unique patterns and relationships of life. Data that is collected is authentic and predictable, which allows researchers to draw conclusions from their findings. For this type of study to work properly, however, there must be procedures in place from the very beginning to remove bias, inaccurate data, and other negative influences.
In return, the data collected has the potential to alter our perspectives in a number of fields.