A prospective cohort study was conducted to assess the relationship between caffeine consumption and the risk of colon cancer in middle-aged women. The study showed that caffeine consumption decreases the risk of colon cancer with a relative risk of 0.83 and p value of 0.04. The fact that the study was conducted specifically in middle-aged women raises most concerns regarding which of the following issues?

Question

A prospective cohort study was conducted to assess the relationship between caffeine consumption and the risk of colon cancer in middle-aged women.  The study showed that caffeine consumption decreases the risk of colon cancer with a relative risk of 0.83 and p value of 0.04.  The fact that the study was conducted specifically in middle-aged women raises most concerns regarding which of the following issues?

Quizplus · Accepted Answer

The generalizability, or external validity, of a study is defined as the applicability of the obtained results beyond the cohort that was studied. External validity answers the question, "How generalizable are the results of a study to other populations?" In this study, the external validity seems to be quite limited due to the restriction of the study population to middle-aged women. In other words, because the cohort is restricted to middle-aged women, the results of the study are applicable only to middle-aged women. This is an important concept when applying the results of observational studies and clinical trials to everyday practice if the original inclusion and exclusion criteria are not reviewed carefully. The other answer options are relevant for internal validity answering the following question: "Are the results obtained in this specific cohort valid?" (Choice A) In this scenario, there is no description of how the study was designed, conducted, and analyzed, so it is not possible to determine whether the internal validity was violated (ie, if bias is present). (Choice C) Within this cohort (middle-aged women), the study could be valid. This property is called internal validity, or validity as generally taught. (Choices D and E) Reliability or reproducibility is the measure of random error. Educational objective: Generalizability or external validity pertains to the applicability of study results to other populations (eg, the results of a study in middle-aged women would not be expected to be applicable to elderly men).

A Prospective Cohort Study Was Conducted to Assess the Relationship