Diet and Nutrition

Hemorrhagic stroke & cholesterol

06/30/1998

Question:

My father recently died at age 87 after a decade-long decline, characterized (his personal physician concluded, post-mortem) by many small hemorrhagic strokes which progressively robbed him of memory, movement and speech. Decades earlier, he had gone on a cholesterol lowering diet to combat (successfully) high blood pressure and high blood cholesterol. Hemorrhagic strokes apparently run in my family. I'm wondering: is there anything in recent research that suggests a connection between ultra-low cholesterol (dietary or in blood) and increased risk of cerebrovascular incidents?

Answer:

You ask an interesting question which required some searching in the library. Sorry for the delay in getting back to you.
In the 1980's, many large studies began publishing data looking at causes of death in individuals with different cholesterol levels. The National Heart, Lung and Blood Institute in 1990 held a conference to review whether there were any significant health risks associated with a low cholesterol level. This conference, and most other articles published, define low cholesterol as a total cholesterol as being less than 160 mg/dl. (Only about 6 % of the population has a cholesterol in this category.)
Although the hazards of high blood cholesterol are widely known, the important role of cholesterol in the body is not as widely publicized. Cholesterol is an essential product serving many functions. It is a key component of cell membranes, serves as a carrier in the blood for important nutrients and some drugs, and serves as a precursor for several hormones. When cholesterol levels are too high, however, they promote atherosclerosis - the build up of plaque in arteries. Thus, high cholesterol levels contribute significantly to coronary artery disease - the number one cause of death in the United States.
Although low cholesterol levels are associated with several illness, low cholesterol is believed to contribute to only one disease entity - hemorrhagic stroke. Individuals with hemorrhagic stroke have small blood vessels in the brain that have weakened walls. This injured blood vessel walls sometimes make an outpouching called an aneurysm. If these aneurysms rupture, bleeding into the brain occurs damaging nerve cells and causing a stroke. Low cholesterol levels seem to aggravate this condition. These types of microaneurysms are usually seen in individuals with high blood pressure. Although certain cancers and other illnesses have been associated with low cholesterol, the disease or another factor causing the disease has also caused a reduction in cholesterol. Thus, in some individuals, a low cholesterol may be a marker for illness. The low cholesterol, however, does not cause these other illnesses.
Because hemorrhagic stroke is relatively rare in this country, the cardiovascular benefits of reducing blood cholesterol levels far outweigh the very small increased risk of hemorrhagic stroke for most Americans. In your case, however, the risk benefit ratio of a low cholesterol level may be different. If you have a cholesterol that is less than 160 and you follow a very low fat diet, you may want to liberalize your fat intake somewhat. Remember, however, that a diet high in saturated fat is not only a risk factor for heart and vascular disease, but may also contribute to cancers of the breast, prostate and colon. If your cholesterol is higher than 160, your cholesterol will probably have little effect on your risk of hemorrhagic stroke. A high cholesterol level, on the other hand, can increase your risk of thrombolic stroke, the most common cause of stroke in the U.S.
To further reduce your risk of stroke, choose healthy habits that promote a normal blood pressure (exercise regularly, limit your consumption of salt and alcohol, eat lots of fruit and veggies - five or more daily, and get plenty of calcium in your diet.) If you are a smoker, quitting will significantly decrease your risk of stroke and many other diseases.
Jacobs David, et al Report of the Conference on Low Blood Cholesterol: Mortality Associations Circulation 86(3): 1046-60 Sept 92
Iso, Hiroyasu, et al Serum Cholesterol levels and Six-year Mortality from stroke in 350,977 men screened for the Multiple Risk Factor Intervention Trial NEJM 320 (14): 904-10 April 89
Law, MR, et al Assessing possible hazards of reducing serum cholesterol British Medical J 308:373-79 Feb 94

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Response by:

Jill Foster, MD
Assistant Professor
Department of Family Medicine
College of Medicine
University of Cincinnati