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(Stroke. 2002;33:321.)
© 2002 American Heart Association, Inc.

Letters to the Editor

Cholesterol and Carotid Stenosis

Kazim Sheikh, MD

US Department of Health and Human Services, Centers for Medicare & Medicaid Services, Kansas City, Missouri

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 represented their HDL-C levels before atherosclerotic disease of carotid arteries had developed. Consequently, the time lag between measuring the baseline attributes and ascertaining the disease was not possible.

It could be argued that a relative increase or decrease in blood cholesterol among cases in this study could have been caused by the disease. This problem with cross-sectional data was addressed by an analysis of the data on cholesterol in the Framingham Heart Study. Although atherosclerotic carotid stenosis was associated with total serum cholesterol and HDL-C . . . [Full Text of this Article]

Ellisiv B. Mathiesen; Kaare H. Bønaa Oddmund Joakimsen

Institute of Community Medicine, University of Tromsø, N-9037 Tromsø, Norway