What is a Longitudinal Study?

A longitudinal study can span years and decades.
A longitudinal study can span years and decades.

Studies are always carried out to understand the aspect of an observational study over a long period. The longitudinal study observes some variables in different subjects either retrospectively or prospectively to determine the association between the occurrence of the changes on the subjects and the factors perceived to have the influence.

What is a Longitudinal Study?

A longitudinal study is one of the research strategies that is observational in nature and pertains repetitive observations of the same subjects over an extended period. The study can last for years and sometimes for decades. It is a common type of study that is applied in sociology, medicine, and psychology.

The longitudinal study gave researchers an opportunity to monitor occurring changes in the selected samples over a period of time.

A number of these studies determine the relationship between the exposure to what is known or what is suspected to be the cause of, for example a disease, its morbidity, and mortality. The subjects exposed to the risk elements are registered together with the unexposed sample that will act as control. They are then monitoring prospectively, and the incidence of the disease occurrence in every factor is estimated. Thus, the estimation of the relative risk, attributable, and incidence rate can be done by making a comparison of the interacting factors.

Types of Longitudinal Studies

There are three distinct types of longitudinal studies: panel, retrospective, and cohort. The panel is a kind of longitudinal study that pertains the use of a sample that represent the groups of subjects mostly draw using a panel service company. The retrospective study uses the already existing information by applying comparison between the old and new statistics to expand the standard knowledge. A cohort study slightly copies the panel study, but it observes the subjects exclusively who shared a common characteristic such as age, geographical region, or a line of work.

Examples of Longitudinal Research

The following are some existing longitudinal studies done by different researchers in various institutions of learning worldwide.

The 1948 Heart Study done in Framingham is a good example. The study involved 5,209 people from Massachusetts who were observed over a period and led to what has been termed the greatest source of knowledge. It established the impacts of diet, over-the-counter medications like aspirin, and exercise on the occurrence of heart conditions. The Framington Heart Study is currently following the participants’ third generation.

In the year 1971, the British Office of Population Censuses and Surveys started a study that meant to observe one percentage of the population. It was to find out the effects of housing and employment status on the occurrence of cancer, and the rate of mortality.

The Genetic Studies of Genius is the most prolonged longitudinal study that still runs. It was started in 1921 by Lewis Terman at the Stanford University to observe the characteristics and development of gifted kids over their lifespan. Lewis’ initial intention was to demystify the belief that gifted teenagers were more vulnerable physically, and tend to move towards inappropriate behavior. His findings indicated that just like the less-privileged children, a gifted kid grows typically just like any other child.

The Human Speechome Project is a determination to monitor and models how a child acquires language during his or her first three years of life. The study was done by the Deb Roy, a professor at Massachusetts Institute of Technology in the institution media laboratory. Interestingly, his son was the only child under the observation with a collection of technology. The data obtained is used to generate what Deb called computational models to provide more insight into the process that ones used to acquire language.

The Grant Study is one of the Harvard Medical School studies that was carried out to determine how adult development and changes initiate occurrence of old age diseases and disorders. The study involved a longitudinal data collection that lasted for 75 years in which 288 mentally and physically fits individuals were picked for the study. The samples were from America, and up to date only men are still going on with the study. They are given a questionnaire every year for evaluation.

Another example is the Canada Longitudinal Study on Aging (CLSA) which followed about 50,000 people for 20 years. The CLSA researchers obtained information on various issues such as medical, social, biological, and economic aspects among others factors. It aimed to establish how the above factors contribute either collectively or individually to the occurrence of the diseases, disorder, or disability.

Advantages of Longitudinal Studies

Every study has some advantages and limitations. One of the advantages of longitudinal studies is the capacity to outline the patterns of every variable at any given time. In this way, one is in a position to understand what the researchers called the “cause-and-effect relationship.” This study can also be used to determine “sleeper effects” that is the links between events that had been studied over time with no clear connections.

Drawbacks of Longitudinal Studies

The fact that this study takes a long time compared to other studies makes it possible to lose one or more participants during the study period. The loss can be occasioned by the death, withdrawal, or contact loss of the participant. In case of reduction of participants in number due to any of the above reasons, the required data is cut down, affecting the research credibility. However, this limitation can be avoided by doing the study retrospectively through the use of existing documents.

Another limitation of the longitudinal study is that the data is always collected only at the definite points; therefore, any changes at the space-periods between succeeding points are not put into consideration.

Lastly, the participants can alter their information to sooth what they think the researcher wanted. However, training of assistant researchers will diminish the possibility of encountering such occasions where participants give wrong information with the sole reason to please the researcher.


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