Role and Limitations of Epidemiology in Establishing a Causal Association


This paper critiques the article written by Eduardo et al. (2004). Eduardo et al. (2004) article aim at evaluating the role and the limitations of epidemiology. At the moment, epidemiological studies are used in the identification of carcinogens not only in the physical environment but also in the chemical and biological environments. This paper will start by identifying research questions, hypotheses and the study design. Thereafter, it will evaluate the strengths and weaknesses of the methodology employed by Eduardo et al. (2004). This paper will also analyze the study’s results. The identification of potential sources of biases and the study’s conclusions will sum up the discussion of this paper.

Research Questions

Epidemiology plays a key role in cancer risk assessments. Cancer policymakers rely heavily on epidemiological approaches because epidemiological studies are vital in the identification and monitoring of the prevalence of cancer in the general population. The advent of molecular epidemiology has boosted the role of epidemiology in the study of cancer since it allows for an accurate exposure assessment. The scope of cancer epidemiology continues to expand. As a result, the researchers sought to answer several questions, which arise due to epidemiology’s ever-increasing scope in oncology. The researchers sought to evaluate the value of epidemiology in the context of all scientific disciplines concerned with cancer risk assessment. The researchers based their study on the fact that although epidemiology has its own limitations, it is a significant tool used in the formulation of policies that govern cancer research. Thus, the researchers strived to find out the extent of the application of molecular epidemiology in oncology.


The study’s hypothesis is “to identify the role and limitations of epidemiology as a methodological discipline concerned with the identification of carcinogens in the physical, chemical, and biological environment” (Eduardo et al., 2004, p. 413).

Study Design

Generally, epidemiology explores the distribution and determinants of disease prevalence in human subjects and the findings from such studies are used to solve health challenges. In addition, epidemiology involves surveillance and research. A number of study designs exist. In this case, Eduardo et al. (2004) used a cohort study. Cohort studies often examine two groups: exposed and unexposed. Most importantly, the researchers employed an ambidirectional cohort study. Usually, cohort study investigators gather information from a number of sources including medical and employment records, and interviews. Other sources include laboratory tests, environmental monitoring and observations. The study conducted by Eduardo et al. (2004) collected information from public health regulatory agencies such as the US Environmental Protection Agency, the World Health Organization’s International Agency for Research on Cancer, and the US National Toxicology Program. In addition, the researchers collected information from scholarly sources. The researchers then used two forms of cancer as examples, that is, stomach and cervical cancers. The researchers evaluated the causes of the aforementioned cancers in an endeavor to substantiate their arguments.

Critique of the Methodology: Strengths and Weaknesses.

The use of cohort studies has a number of advantages and disadvantages. Causation cannot be generally be proved with cohort studies because they are observational and do not involve interventions. However, because they follow a cohort of patients forward through time, they possess the correct time sequence to provide strong evidence for causes and effects. The length of time required in a cohort study depends upon the problem studied. With diseases that develop over a long period of time, or with conditions that occur following long-term exposure to some causative agents, many years are needed. Extended time periods make studies costly. They also make it difficult for investigators to argue causation, owing to the fact that events occurring in the intervening period may have affected the outcome. However, it should be noted that cohort studies are the best observational study design for investigating the causes of a condition, the course of a disease, or risk factors.


The researchers found out “that what prevails today is an operational definition of cause, which incorporates the criteria required in settings, depending on the type of carcinogenic mechanism being studied and its particular set of specific circumstances to ascertain exposure and endpoints” (Eduardo et al., 2004, p. 417). In addition, the researchers also learnt that “decisions concerning the carcinogenicity of specific exposures must entertain both scientific and public health issues as a dynamic process that is constantly updated as new knowledge from insightful and more valid epidemiologic studies becomes available” (Eduardo et al., 2004, p. 417). The researchers compiled findings from previous studies and analyzed them prior to giving their conclusions. Since the study was purely observational, the researchers did not use any analytical software or technique. Their conclusions were based merely on the data they collected from the aforementioned sources.

Potential Sources of Bias

Since it is a historical study in nature, one potential source of bias is that the researchers cannot control the outcome of the previous studies. Eduardo et al. (2004) used various previous studies to substantiate their hypothesis. Therefore, they were not in a position to influence the data presented in the scholarly work they quoted.


The researchers note that “although epidemiological studies have been heightened by the invention of molecular epidemiology and thus boosting gene-environment interactions and risk exposure assessment, they remain susceptible to vicissitudes of learning via controlled observations of the joint distribution of exposure and disease in human populations” (Eduardo et al., 2004, p. 423). Eduardo et al. (2004) argue that the use of molecular epidemiology at a single point in time does not guarantee appropriate policy decisions. This is exemplified by the drawbacks encountered during the initial large-scale molecular epidemiological studies of cervical cancer and the Human pappiloma Virus. The researchers conclude that molecular epidemiology needs to be updated frequently in order to “enhance its validity and ensure the timely discovery of carcinogens and appropriate prevention actions” (Eduardo et al., 2004, p. 423).


Eduardo, E. L. (2004). Role and limitations of epidemiology in establishing a causal association. Seminars In Cancer Biology, 14, 413-426.

Find out your order's cost