Midterm Exam

1. What do we mean by ‘the critical window of exposure’ of a dietary factor in relation to a disease outcome? (2pts)

2. Why may a blood biomarker of a nutrient not be closely correlated to the usual intake of said nutrient? Explain at least 4 reasons. (4pts)

3. Factor analysis separates individuals into mutually exclusive groups based on dietary intake. True or false? (1pt)

4. Use the table below to answer the following questions:

a) What proportion (%) of participants were NOT misclassified when using vitamin C from diet only? Show your work. (1pt)

b) Based on this information, if you were to analyze the association between vitamin C and cardiovascular disease using data from this sample, would it be more appropriate to conduct the analyses using measures of vitamin C from diet + supplements or using vitamin C from diet only? Why or why not? Justify your answer. (2pts)

5. The table below shows the mean Healthy Eating Index 2010 scores for participants and nonparticipants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) before and after the WIC food package was revised in 2009. Use the table to answer the following questions:

a. What are the mean Healthy Eating Index 2010 scores for WIC participants before and after the WIC food package change? (1pt)

b. What do these scores tell you about the diet quality of WIC participants after the WIC food package change relative to before the change? (2pts)

6.  Answer the following questions for each type of observational study design listed below. (5pts)

7. You are investigating the association between childhood consumption of dairy and a rare autoimmune disorder among adults. Which study design AND dietary assessment method would you use to conduct this research? Justify your answer. (3pts)

8. Do the following scenarios represent random or systematic error? Justify your answers. (3pts)

a. Height was consistently 3cm higher than the true height:

b. A research assistant took 3 heights, and they were slightly different:

c. FFQ did not differentiate between citrus fruits and other fruits:

9. Which of the following statements are true? Select all that apply. (1pt)

a. Systematic error reduces validity

b. Systematic error reduces precision

c. Random error reduces validity

d. Random error reduces precision

10. The repeated measures taken on a sphygmomanometer (blood pressure monitor) are exactly the same within a period of five minutes. Does this information mean that the tool is precise or that it is accurate? (2pts)

11. Several research questions are listed below. For each of the questions, is it more appropriate to use a biomarker or dietary intake to assess the dietary exposure of interest? Justify your answer. If you choose a biomarker, explain why a biomarker is appropriate. If you choose dietary intake, explain why dietary intake is appropriate. (3pts)

a. What is the association between fruit and vegetable intake and risk of stroke?

b. What is the association between intake of calcium and the development of type 2 diabetes in adolescents?

c. What is the association between maternal vitamin D status during pregnancy and offspring birthweight?

12. What are two strategies to reduce random error (and/or the effect of random error) in a study examining diet-disease associations? Explain your answer. (4pts)

13. Use the table below (Table 5) from the Women’s Health Initiative Observational Study to answer the following questions:

a. What is the independent variable? (1pt)

b. What is the dependent variable? (1pt)

c. The range of caffeine intake in quintile 5 is 315-794 mg. Assuming that 794 mg caffeine intake is considered an outlier, will it influence the results in this analysis? Justify your answer. (2pts)

d. This study found no significant association between the dietary exposure and health outcome. Assuming that there is a true association, what are some potential reasons that a significant association was not detected? Discuss at least 4 reasons. (4pts)

14. Provide one reason that researchers exclude participants with extreme (very high or very low) energy intakes when studying diet-disease associations in nutritional epidemiology? (2pts)

15. Use the table below (table 2) from the Nurses’ Health Study to answer the following questions:

a. Looking at model 3, what is the association between each dietary exposure and type 2 diabetes, comparing the results of quintile 5 versus quintile 1? Using full sentences, please comment on the direction and magnitude of any significant associations you identify (for non-significant associations, you can simply state that there is no association). (6pts)

b. Is the p-for-trend significant for model 3 for any of the dietary exposures? What does this indicate? (3pts)

16. Use the table below (Table 3) from the Singapore Chinese Health Study to answer the following questions:

a. List the different approaches used to measure diet quality in this analysis. (3pts)

b. The approaches used to measure diet quality in this analysis are data driven. True or false? (1pt)

c. Provide at least one rationale for conducting an analysis using diet quality instead of a single nutrient/food group analytical approach. (2pts)

17. Use the table below (Table 3) from the Nurses’ Health Study to answer the following questions:

a. Is it correct to control for total energy intake in this analysis? Why or why not? Justify your answer. (2pts)

b. Looking at model 3, what is the association between each dietary exposure and ischemic stroke, comparing the results of quintile 5 versus quintile 1? Using full sentences, please comment on the direction and magnitude of any significant associations you identify (for non-significant associations, you can simply state that there is no association). (4pts)

c. For each dietary exposure, is the p-for-trend significant for model 3? What does this indicate? (3pts)

d. Based on these findings, what public health recommendations would you make regarding grain consumption in the context of ischemic stroke among women? Justify your answer. Please do not simply restate the results, I want to know what you think the public health implications of the results should be. (2pts)