High-Density Lipoprotein Cholesterol and Risk of Stroke

To the Editor: Dr Sacco and colleagues¹ compared poststroke cholesterol levels in stroke patients with prestroke levels in control subjects, and found an inverse association between high-density lipoprotein cholesterol (HDL-C) and the risk of ischemic stroke. The main problem with this study was its use of cross-sectional data on cholesterol, because acute cerebral infarction could have, somehow, resulted in reduced blood HDL-C. Such a difference could have biased the case-control comparisons. Although the authors assured the "stability of lipids" after stroke, it was not established that the poststroke HDL-C levels in the study cases represented their HDL-C levels before atherosclerotic disease of cerebral and precerebral arteries had developed. The time lag between measuring the baseline attributes and ascertaining chronic diseases was not possible in this study. This is a major limitation of cross-sectional data on variables with changing values in epidemiological research of the risk factors for chronic diseases.