A Prospective Research Looks at the Link Between Frequent Antioxidant

A prospective research looks at the link between frequent antioxidant supplement usage (vitamins C and E) and the risk of stroke in males aged 40-60 who are physically active. The study compares the risk of stroke among men who used antioxidant supplements for 5 years to the risk of stroke among men who did not take antioxidant supplements for 5 years, as compared to a control group of men who never took antioxidant supplements. When compared to the reference group, men who consumed antioxidant supplements for 5 years and men who consumed antioxidant supplements for 5 years had stroke relative risks of 0.95 (p = 0.45) and 0.75 (p = 0.01) , respectively. The study's findings were modified to account for baseline variations in healthy habits and  overall health.   Which of the following factors most likely explains why the relative risk of stroke is lower with longer antioxidant use?

A) Accumulation effect
B) Lead-time bias
C) Observer bias
D) Rare disease assumption
E) Selection bias