Article Citation: Lee IM, Cook NR, Gaziano JM, Gordon D, Ridker PM, Manson JE, Hennekens CH, Buring JE. Vitamin E in the primary prevention of cardiovascular disease and cancer: The Women’s Health Study: a randomized controlled trial. Jama. 2005 Jul 6;294(1):56-65.
Directions: Please answer the following questions from the Lee et al. study listed above. The citation is given above. It is not required to cite the article, however if you cite outside material please use AMA style. Question 1 is already answered.
Questions:
1. What makes the randomized controlled trial (RCT) the “gold standard” of study designs? What is the key feature that makes it the most robust design?
RCT’s are considered prospective studies that measure the effectiveness of a new intervention or treatment, reducing bias and provides a tool to examine the cause-effect relationships between an intervention and outcome. The act of randomization helps balance the characteristics of observed and unobserved participants which allows attribution of any differences in the outcome to the study intervention which is not possible in any other study design making it the most robust study design.
2. What was the main exposure and main outcomes in the study?
3. How many people were successfully recruited to participate in the study and how were they recruited?
4. What were the selection criteria for the people in the study? In other words, what characteristics did all of the people in the study have in common?
5. What does Table 1 tell us about the intervention group and the control group? Were they different or the same? How do you know?
6. Calculate the relative risk (Show your work and round your final answer to two (2) decimal places) of having a major cardiovascular event among those who were exposed to vitamin E and among those who were not exposed. (Hint: you’re only calculating one statistic, which is the RR. See Table 2.) Does the relative risk you calculated match the relative risk reported in Table 2?
7. Table 3 shows the relative risks of cardiovascular disease and cancer according to baseline characteristics in the women’s health study. Was age an effect modifier in the relationship between vitamin E and major cardiovascular events (assuming age was not a confounder)? How do you know whether age was an effect modifier or not based on the information presented in Table 3?
8. Write a conclusion for the relationship between vitamin E and major cardiovascular event for people aged 65+ (See Table 3). Use the RR in your statement just like we have done previously.
9. Did the authors use intention-to-treat analysis or actual treatment received analysis? Why was it important to conduct the analysis in the way the authors chose? What did this type of analysis ensure for the researchers about any confounding variables?
10. Do you agree with the author’s conclusions about not recommending vitamin E to healthy women? What group might benefit?
