Environmental Toxicology Diary

You have already learned the basic and definition of epidemiology study from previous post. There are two kinds of methods available for epidemiology study, retrospective and prospective study. These two methods provide a very different approach and behavior during the study. This post will only describe characteristic of epidemiology retrospective study.

One keynote you should pay attention about retrospective study is that it studies the past. The goal is still the same to find out the causative agent and factors related to the observed effects. The information gathered in this method is from the past time, thus it probably cross in your mind about the accuracy of such data. Indeed, it is often difficult to discover the relationship of a observed effects and the factors. Usually the information from the past really depends on the subject being studied, age, race, memory ability.

Basically, epidemiology retropective studies compare the incidence of illness in two or more groups of people. One who develop a disease while the other is control. Since past information is being collected, thus reconstruction of what had happened in the past is usually employed, to learn what toxic chemicals involve with this effect. So this type of study look for the effect after exposure has ocurred and disease has developed.

Retrospective study is usually quicker and cheaper, since it collects past information, create groups. But of course the consequence is possible inaccurate information. The group who develops disease or illness is compared with the group without disease. Individuals of each group will of course have same thing in common such as gender, age, daily habits or even same environment conditions. The choosing of same characteristics is that to eliminate variables that unrelated to the occurrence of the disease.

More details about the group. One group is individuals with disease, and another without disease. These two groups are further divided based on the occurence of disease. For example, in one group with disease, split to two part, one which individuals exposed by suspected causative agent and one which indiduals were not exposed. The analogue applies for controlled group (without disease).

There are disadvantages using this type of method as already mentioned briefly above. Information depends on past information, thus it is possible that these methods may be incomplete, inaccurate and confounding factors (related to the individuals, sex, age, ethnic and personal habit) may not be identified. The methods used usually like medical records, employment histories or questionnaires. Since the study may require a long time, the collection methods for data that have been used higher chance are different and vary, therefore, the data may not be reliable.

So in short, the disadvantages of epidemiology retrospective studies include
1) incomplete records of exposure
2) inability to completely identify confounding factor
3) high susceptibiligy to bias due to data are obtained from recall process
4) only a weak to moderate association can be established between disease and causative agent

The advantages include
1) quicker to study, since the disease has already occurred
2) less expensive, no need to follow individuals and wait until illness occurs

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