Lipid profile of stroke risk

The chance of suffering a stroke increases dramatically with age, making screening for potential risk factors an essential part of elder healthcare. Clinicians know that total and LDL cholesterol are two such factors, but less attention has focused on how levels of HDL cholesterol affect stroke risk. Now, a new study published in the Journal of the American Medical Association reports that HDL cholesterol was a powerful predictor of ischemic stroke in a multi-ethnic, older population.

High HDL linked to fewer ischemic strokes

Researchers at Columbia University in New York matched 539 men and women who had suffered an ischemic stroke with 905 healthy controls. Two-thirds of the participants were age 65 or older. All provided detailed health and demographic information and were tested for fasting levels of serum cholesterol and triglycerides. After controlling for factors known to affect stroke risk and adjusting for LDL cholesterol and triglycerides, the scientists found that serum HDL cholesterol levels were inversely proportional to risk of ischemic stroke.

Compared with the participants who had HDL cholesterol levels lower than 35 mg/dL (0.9 mmol/L), the odds ratio for stroke risk in those with HDL levels higher than this level was 0.50 (95% CI, 0.37-0.70). With HDL levels over 50 mg/dL (1.3 mmol/L), the odds ratio dropped to 0.29 (95% CI, 0.19-0.44). The results were most pronounced in participants older than age 65.

Although a definitive pathway has yet to be determined, the authors propose several possible ways that HDL cholesterol may protect against ischemic stroke. HDL may hinder the oxidation of LDL cholesterol, possibly by delivering antioxidants to LDL particles within the endothelium. HDL likely also protects blood vessels by transporting LDL cholesterol to the liver for recycling.

Ethnicity may play a role

The authors of this paper acknowledge that other studies, including the long-running Framingham Heart Study, have found little association between total serum cholesterol or HDL cholesterol and risk of cerebral infarction. But not all strokes are due to atherosclerosis, so not all cases will be equally tied to lipid profile as a predictive factor. The population in this current study included a large percentage of blacks and Hispanics, two ethnic groups with a greater-than-average risk of death from atherosclerosis-related stroke. It is possible, then, that the effect of HDL cholesterol status was particularly pronounced in this analysis.

Prudent advice to patients

The role of lipids as a factor in stroke risk is still under study, but these data suggest that maintaining a healthy cholesterol profile--low LDL and high HDL--is key to controlling damage from ischemic stroke.

It's important to point out to patients that they are not necessarily 'stuck' with unhealthy levels of HDL cholesterol. Exercise, weight control, moderate alcohol consumption, smoking cessation, and statin drugs can all help maintain a good ratio between LDL and HDL cholesterol.