Cholesterol and Carotid Stenosis

Abstract

To the Editor: In a case-control study, Dr Mathiesen and colleagues1 compared the blood levels of high-density lipoprotein cholesterol (HDL-C) in 216 patients with carotid stenosis with those in 223 subjects who were free from the disease. They found an inverse association between HDL-C levels and the risk of carotid stenosis, a precursor of ischemic stroke.1 The authors acknowledged that the main problem with their study was its use of cross-sectional data—the HDL-C levels among the cases were measured at the time of the diagnosis of carotid stenosis. Consequently, the postdisease levels of HDL-C in cases were compared with the predisease levels in control subjects. If the study risk factor had a value that could not change, such as a blood group type, the case-control comparisons would not have been biased. However, blood cholesterol is a variable whose value can change due to medications or it can physiologically change over time. This case-control study could not establish that the HDL-C levels in cases at the time of diagnosis …