What is longitudinal research and what is it for?

There are investigations that cannot be addressed directly, due to the temporal order and the need to measure evolutions, allowing through them to make solid interpretations. For this type of designs, methodologies such aslongitudinal research are applied.

In the following article, we will talk about what longitudinal research is, types, elements and their main characteristics.

What is longitudinal research?

Longitudinal research is defined as that which is carried out through continuous or repeated measurements, for statistical perspectives and thatfrom the epidemiological perspectives the longitudinal investigation is a function of cohorts.

These types of studiesare also recognized as evolutionary studies, so it requires attention to analyze the variables.

To highlight: It is important to mention that although the conceptualization is somewhat deficient, it is due to the difficulty of obtaining an acceptable one for its different applications, even so, Chin for 1989 in his workLongitudinal studies: objectives and ethical considerations, summarized it as equivalent to a follow-up(1).

Characteristics of longitudinal research

For a better understanding of how this type of research develops, we will mention below different characteristics that cover the process of its development and operation.

It is a research method

As its name indicates, it is a research methodology that is responsible for evaluating data collected over a period of time, for the realization of observable means that subsequently proceed to analyze and obtain the required information.

It allows to measure phenomena in a specific time

This type of research is characterized by evaluating the components in periods of time and verifying the data and possible evolutions. It is often applied in medicine for treatments or to summarize the general characteristics of the study and its units.

To highlight: In an article published by the English Journal of Public Health on Longitudinal studies: concept and particularities, it is mentioned that these times are applied to conduct observational events for follow-up (2) .

Allows obtaining information on change processes

The processes of changes are reflected in the collection of periodic data and in the verification with those previously obtained. In this way, a relation and comparison is made between the evolutions that have taken place.

In fact, it is characterized by allowing the ability to demonstrate processes of progress in medical fields, (treatments or diseases) social (poverty and development) among others of the wide range of studies to which it can be applied.

Provides qualitative and quantitative results

This type of study is commonly focused and oriented towards obtaining quantitative analysis, but it has the capacity and facility to also obtain qualitative ones.

In qualitative research, they are responsible for making inferences regarding change based on its determinants and its potential consequences. Above all, it is applied in development processes such as socialization and personal journeys.

While on the quantitative side, continuous measures are used to directly track individual individuals.

It can last years or decades

Time frames may vary, depending on the scope of the investigation. They tend to be characteristically long and through their duration, it is that the data is collected from the same individuals (it should be noted) to make the inferences.

It is the opposite of cross-sectional studies.

The cross-sectional study is defined as one of the observational type, which evaluates the population but at a single point in time,examining the reference with variables of interest. The single definition opens the understanding of the great difference that exists by being based only on a punctual interval.

They are both defined through their temporal elements, plus the transversal ones belong to a single determined moment of time. In the INV HEALTH article on types of studies, they mention their applications to examine characteristics or differences between variables at a specific moment (3) .

It is carried out in various sciences and business areas

They are usually used mainly in health areas, although they are capable of studying phenomena in psychology, education, sociology, behavior, among many others.

It takes time and money to do it.

It is considered a disadvantage, due to the amount of money required to carry it out. They are large investments, both economic and time, to be able to develop them correctly with all the exploration and valuation that it requires.

Sometimes the data is incomplete

The loss of subjects or data influences these aspects , since the researcher in many cases cannot control the elements that play against the development of the study.

Types of longitudinal research

Longitudinal research can be classified based on certain studies that we will mention below. Faced with their distinctions, their type of design and approach influences.

Retrospective study

It is that type of study that analyzes the present time, but with data from the past. It begins before the events to be studied happen and in many cases its objective is to compare and control certain elements, based on its multiple advantages.

Study Panel

It is considered quite particular, where there is a population sample that is investigated after certain specific time intervals.

To highlight: In research such as Longitudinal panel designs: data analysis alternatives, it is established how its use is focused on obtaining evidence in a study of temporal effect, to see the relationship between defined variables (4)

Cohort Study

This is understood as an analytical investigation (whether retrospective or prospective) to make comparisons, follow-up, incidence, among others. These studies focus on the presence or absence of events to be observable and analyzed.

Elements of longitudinal research

Longitudinal research has different elements that structure its development. The same factors will be mentioned and described below for your better understanding.

longitudinal data

They are those data that imply existence in repeated measures (more than two) throughout a follow-up. In other words, they are the information that will be processed, such as that collected through time intervals, for verification or comparison.

Timeslots

They are the periods or points within which the investigation takes place. They constitute the data collection intervals, thanks to which the changes in the elements are determined.

Observed elements

The observed elements are the objects of study, being these phenomena or even the different individuals that will be evaluatedand with their disciplined follow-up throughout the investigation. They are also recognized as targets.

Trend

The trend can also be recognized as a response curve or profile and refers to the set of possible responses of the evaluated unit. They are the ones that allow analysis over time and are the ones that pay attention to the evaluated population.

Key takeaways

• Longitudinal research is one that is carried out through continuous or repeated measurements, for statistical perspectives and that from epidemiological perspectives, longitudinal research is based on cohorts.
• Longitudinal research has different characteristics that cover the process of its development and operation, among them: it allows obtaining information on change processes, it provides qualitative and quantitative results, it can last for years or decades, which is why it also requires time and money; and in some cases the data is incomplete.
• There are three types of longitudinal research, they are: Retrospective study, analyzes the present time, but with data from the past. Study panel, in this there is a population sample that is investigated after certain specific time intervals. And finally the cohort study that focuses on the presence or absence of events to be observable and analyzed.
• Longitudinal research has four elements that structure its development, they are: Longitudinal data, time intervals, observed elements and the trend, which refers to the set of possible responses of the evaluated unit.