Epidemiology 5

All of the following questions are in relation to the following journal article which is available on Moodle: Parr CL, Magnus MC, Karlstad O, Holvik K, Lund-Blix NA, Jaugen M, et al. Vitamin A and D intake in pregnancy, infant supplementation and asthma development: the Norwegian Mother and Child Cohort. Am J Clin Nutr 2018;107:789-798.

QUESTIONS: Questions 1-4 pertain to the crude and adjusted relative risk estimates in table 5. (Note: use the second crude RR called RR3).

1. Do the confounding factors attenuate the increased risk for asthma by daily multivitamin supplementation by infants?

2. Calculate the amount of confounding for daily intake of multivitamins.

3. Do the confounding factors attenuate the protective effect of daily vitamin D only supplementation?

4. Are any of the effect estimates in table 5 unaffected by the confounding factors? If so, which ones?

5. Do the authors consider the same potential founders in table 3 as they do in table 5?

6. Do you draw a different conclusion from the adjusted RR for total vitamin D intake on risk of asthma than you do from the crude results in Table 3?

7. How might the investigators have used restriction to control for the confounding of birthweight in this study? How would this decision effect the validity of the study sample?