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Statins and incidence of perioperative mortality in patients undergoing major noncardiac vascular surgery.

To the Editor:

Poldermans et al1 published a retrospective study in which they found evidence that statin use reduces perioperative mortality in patients undergoing major vascular surgery. We have, however, some methodological concerns pertaining to selection, information, and confounding bias that were not discussed but that may have harmed validity.

First, the authors do not provide data on length of hospital stay. Assuming a protective effect of statins, the identification of cases determined as patients who died in-hospital may have led to nonrandom misclassification because healthier patients who die after leaving the hospital can never become cases. It would have been better had the authors taken a fixed time window.

In the design, the type of surgery and calendar year were the basis of stratification. This may have introduced confounding …