Vitamin supplementation on the risk of XXXX : results from the MEGA case-control study.

@entity1 @entity1150 @entity49 @entity1151
BACKGROUND: Whether vitamin supplements decrease @entity49 risk is controversial. Previous reports did not all take confounding fully into account, either by randomization or by extensive adjustment. OBJECTIVE: The aim of our study was to determine whether vitamin supplementation decreases the risk of @entity49 . DESIGN: A large case-control study included 2506 @entity1 with @entity49 , 2506 partner controls, and 2684 random-digit dialing (RDD) controls. When @entity1 were compared with RDD controls, unconditional logistic regression was used to calculate ORs with 95% CIs. When @entity1 were compared with partner controls, conditional logistic regression was used, providing further adjustment for unmeasured confounding. RESULTS: Vitamin use yielded a 37% lower risk of @entity49 than no vitamin use (OR: 0.63; 95% CI: 0.57, 0.70) when comparing @entity1 with RDD controls. Adjustment for several putative confounders did not change the estimate (OR: 0.68; 95% CI: 0.61, 0.77). The fully adjusted ORs for vitamin A, vitamin B-6, vitamin B-12, folic acid, vitamin C, vitamin D, vitamin E, and multivitamin use were in the same range. However, when @entity1 were compared with partner controls, ORs attenuated to unity. Results were similar for provoked and unprovoked events, as well as for @entity1150 and @entity1151 . CONCLUSIONS: After extensive adjustments, vitamin supplementation was no longer associated with a decreased risk of @entity49 in this study. Previous positive results may have been spurious as a result of uncontrolled confounding.
