Identifying Independent Risk Factors for Stroke


The December 11, 2001, issue of Circulation, the journal of the American Heart Association (AHA), published a study by Tanne et al. of Sheba Medical Center in Tel Hashomer, Israel. It reported on more than 11,000 individuals with coronary heart disease but no previous history of stroke or transient ischemic attacks (TIA). All were followed for six to eight years for risk of stroke or TIA. A stroke or TIA occurs when a blood clot or narrowed artery blocks blood flow to the brain. During the study, 487 individuals experienced such an incident. They were found to have triglyceride levels that were higher and HDLs ("good" cholesterol levels) that were lower than those of individuals who did not develop stroke or TIA.
The conclusion of the researchers was that triglycerides greater than 200 mg/dL increased the risk of having a stroke by 30 percent, independent of other risk factors. The authors suggested that physicians should pay closer attention to triglyceride levels. More effective screening and detection of high triglycerides and treatments to modify this stroke risk factor could further reduce the clinical and public health burdens of stroke.
The authors also suggested that triglyceride levels should be used to identify people at risk for ischemic stroke. Moreover, they recommended lowering risk by making lifestyle changes such as eating a low-fat diet, losing weight and exercising regularly. They also pointed out that cholesterol-lowering drugs can reduce levels of triglycerides. A representative of the AHA was also quoted as suggesting a low-fat diet and exercise to lower triglycerides below 150 mg/dl, its recommendation for healthy levels.
A number of prior studies have similarly identified high triglycerides and low HDL levels as risk factors for coronary heart disease or ischemic heart disease. Austin et al. did a meta-analysis of 17 population-based prospective studies of triglycerides as cardiovascular risk factors. (1) Manninen et al. studied the joint effects of serum triglyceride and LDL cholesterol and HDL cholesterol concentrations on coronary heart disease risk in the Helsinki Heart Study. (2) Stavenow et al. researched the influence of serum triglyceride levels on the risk for myocardial infarction in over 12,000 middle-aged men. (3) Assman et al. studied the incidence of coronary heart disease events according to serum LDL ("bad") cholesterol and triglyceride concentrations. (4) Jeppesen et al. looked at triglyceride concentration and ischemic heart disease as an eight-year follow-up in the Copenhagen Male Study. (5) Miller et al. found that low HDL levels and high triglyceride levels were found in subjects who developed new coronary events. (6) Gaziano et al. measured fasting triglycerides, HDL lipoprotein and risk of myocardial infarction. (7) In all of these studies as well as several others looking at similar parameters, triglycerides were indicated as being an independent risk factor for heart disease and/or stroke.
The missing link is the clinical application of a controlled carbohydrate nutritional approach to modify a high triglyceride level. Several studies have verified what clinicians have seen in practice: Restricting carbohydrate consumption, with or without calorie restriction, can significantly lower triglyceride levels. Abassi et al. examined high-carbohydrate diets, triglycerides and coronary heart disease risk. (8) Volek et al. (9), Sondike et al. (10) and Yancy et al. (11) all verified what Reissel studied decades ago. (12) When carbohydrate intake is limited, triglyceride concentrations decrease significantly. Despite these findings, both the researchers for this current study as well as representatives of the AHA continue to recommend a low-fat diet for managing high triglyceride levels.
Using a controlled carbohydrate regimen such at the Atkins Nutritional ApproachTM, one can significantly reduce triglyceride levels, increase HDL levels and improve other risk factors for coronary heart disease and stroke, including blood pressure and weight control.
Selected References
1.    Austin, M.A., Hokanson, J.E., Edwards, K.L., "Hypertriglyceridemia as a Cardiovascular Risk Factor," The American Journal of Cardiology, 81(4A), 1998, pages 7B-12B.
2.    Manninen, V., Tenkanen, L., Koskinen, P., et al., "Joint Effects of Serum Triglyceride and LDL Cholesterol and HDL Cholesterol Concentrations on Coronary Heart Disease Risk in the Helsinki Heart Study: Implications for Treatment," Circulation, 85, 1992, pages 37-45.
3.    Stavenow, L., Kjellström, T., "Influence of Serum Triglyceride Levels on the Risk for Myocardial Infarction in 12,510 Middle Aged Males: Interaction with Serum Cholesterol," Atherosclerosis, 147, 1999, pages 243-247.
4.    Assmann, G., Schulte, H., Funke, H., et al., "The Emergence of Triglycerides as a Significant Independent Risk Factor in Coronary Artery Disease," European Heart Journal, 19(Supplement M), 1998, pages M8-M14.
5.    Jeppesen, J., Hein, H.O., Suadicani, P., et al., "Triglyceride Concentration and Ischemic Heart Disease: An Eight-Year Follow-Up in the Copenhagen Male Study," Circulation, 97(11), 1998, pages 1029-1236.
6.    Miller, M., "Is Hypertriglyceridaemia an Independent Risk Factor for Coronary Heart Disease? The Epidemiological Evidence," European Heart Journal, 19(Supplement H), 1998, pages H18-H22.
7.    Gaziano, J.M., Hennekens, C.H., O'Donnell, C.J., et al., "Fasting Triglycerides, High-Density Lipoprotein, and Risk of Myocardial Infarction," Circulation, 96(8), 1997, pages 2520-2525.
8.    Abbasi, F., McLaughlin, T., Lamendola, C., et al., "High Carbohydrate Diets, Triglyceride-Rich Lipoproteins, and Coronary Heart Disease Risk," The American Journal of Cardiology, 85, 2000, pages 45-48.
9.    Volek, J.S., Gómez, A.L., Kraemer, W.J., "Fasting Lipoprotein and Postprandial Triacylglycerol Responses to a Low-Carbohydrate Diet Supplemented with N-3 Fatty Acids,"Journal of the American College of Nutrition, 19(3), 2000, pages 383-391.
10.    Sondike, S.B., Copperman, N.M., Jacobson, M.S., "Low Carbohydrate Dieting Increases Weight Loss but not Cardiovascular Risk in Obese Adolescents: A Randomized Controlled Trial," Journal of Adolescent Health, 26, 2000, page 91.
11.    Yancy, W. S., Bakst, R., Bryson, W., et al., "Effects of a Very-Low-Carbohydrate Diet Program Compared With a Low-Fat, Low-Cholesterol, Reduced Calorie Diet," October 7, 2001, North American Association for the Study of Obesity Annual Meeting, Quebec City, Canada.
12.    Reissell, P.K., Mandella, P.A., Poon-King, T.M.W., et al., "Treatment of Hypertriglyceridemia," The American Journal of Clinical Nutrition, 19, 1966, pages 84-98


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