Introduction
Case-control studies and cohort studies are both categories of observational studies and are the most important types of study designs that can serve either similar or different purposes. If designed effectively, observational studies are able to provide results that are similar to the results achieved in randomized controlled trials, putting forward a view that observational studies are not as effective. Both case-control studies and cohort studies are effective in evaluating the connections that exist between a condition and exposure (Song & Chung, 2011).
When it comes to dental practice, cohort studies are commonly used for studying a risk factor of a particular event. For example, researchers can study a risk factor of exposure to sugary drinks and chocolate as well as the subsequent appearance of caries signs. Contrary to the cohort study design, case-control studies explore a particular disease or a condition to find out whether some risk factors can be associated with it. In cohort studies, the end condition is not predetermined while in case-control studies the outcome is already known. Despite that cohort studies can be conducted retrospectively, the majority of them are conducted prospectively so that the slightest changes can be examined within a course of a particular time period. Case-control studies can be conducted in retrospect because the outcome is already known, so there is no need for studying the changes that occurred over a set period of time.
Cohort Studies
Cohort studies relate to a group of people who have been followed by researchers for a long period of time. In the process of conducting a cohort study on any health topic, the study population or outcomes are identified with the use of exposure to a particular event than is then followed for a set period of time for the identified outcome to occur. Because the exposure to an event is already predetermined before the appearance of an outcome, cohort studies are observational studies that are limited to a particular period of time, and therefore, are able to provide strong evidence to support or disprove the initial hypothesis.
For example, a cohort study design was used by Arora, Scott, Bhole, Do, Schwarz, and Blinkhorn (2011) for finding connections between early childhood feeding practices and the development of dental caries in preschool children. Mothers were invited to participate in the study after giving birth to a child (Arora et al., 2011). Data on the feeding practices implemented by mothers, alongside the information on dental practices was gathered through telephone interviews every 4 months since birth. At 2 and 5 years old, children went through a dental assessment to determine the main outcome measures (Arora et al., 2011). Therefore, cohort studies are best implemented when the outcome is identified in accordance with the subjects being exposed to a particular event. Subjects with already identified outcomes are not included in cohort studies because the aim is to conduct examinations and following-up to find connections between the possible outcome and the exposure to an event. In the discussed study, the dental behavior and early childhood feeding practices were associated with dental caries in preschool children; Arora et al. (2011) used the cohort study design so that subjects’ conditions could be assessed for a long period of time.
Case-Control Studies
Case-control studies are observational studies in which subjects are identified by the status of the outcome as well as the investigation’s outside. For example, outcomes may include whether study subjects had gone through surgery or were diagnosed with a particular disease. With the identification of the outcome status, the subjects of the study were put into different categories for selecting the subjects with no signs of the identified outcome but those that came from the same population. The process of data collection occurs through interviews, surveys, or records abstractions. In comparison with a cohort study design, case-control studies are effective for investigating unusual and unique outcomes or outcomes that have a long period of latency.
Case-control studies can be effectively used in dentistry because they are quick and inexpensive for implementation, especially when it comes to studies of unique conditions that have not been previously studied. Furthermore, case-control studies are suitable for studying rare dental conditions and diseases that have been selected for assessment and research. For example, a study conducted by Memon, Godward, Williams, Siddique, and Al-Saleh (2010) investigated the usage of dental x-rays and the risk of thyroid cancer. The case-control study design was suitable for investigating the topic of dental x-rays and their effect on the development of thyroid cancer due to the uniqueness of the issue. Additionally, case-control studies were helpful for conducting a conditional logistic regression analysis as well as the population-based case-control interviews among thyroid cancer patients. Therefore, case-control studies can be effectively implemented when subjects of studies have already been identified according to a particular outcome.
References
Arora, A., Scott, J., Bhole, S., Do, L., & Blinkhorn, A. (2011). Early childhood feeding practices and dental caries in preschool children: A multi-center birth cohort study. BMC Public Health, 12, 11-28.
Memon, A., Godward, S., Williams, D., Siddique, I., & Al-Saleh, K. (2010). Dental x-rays and the risk of thyroid cancer: A case-control study. Acta Oncologica, 49(4), 447-453.
Song, J., & Chung, K. (2011). Observational studies: Cohort and case-control studies. Plastic and Reconstructive Surgery, 126(6), 2234-2242.