LDL cholesterol increases the risk of heart disease and ischemic stroke, but in patients with very low levels of “bad cholesterol,” hemorrhagic stroke may actually increase.
Pamela M. Rist, ScD
Low-density lipoprotein (LDL) cholesterol is known as “bad cholesterol” for good reason. High levels of LDL cholesterol can lead to a higher risk of heart attack and stroke. However, new research suggests that when it comes to hemorrhagic stroke, having a very low level of LDL cholesterol can be a problem.
By far, the most common type of stroke is ischemic stroke, which occurs when a blood vessel supplying blood to the brain becomes obstructed. According to the American Stroke Association, 87% of strokes are ischemic.
However, hemorrhagic strokes can be equally concerning. These occur when weakened blood vessels rupture, causing bleeding into the brain.
Pamela M. Rist, ScD, of Brigham and Women’s Hospital and Harvard Medical School, and colleagues wanted to gain a better understanding of the links between lipid levels and hemorrhagic stroke. They constructed a prospective cohort study of 27,937 women who were enrolled in the Women’s Health Study, all of whom were 45 years of age or older. The Women’s Health Study was a major study that ran from 1993 to 2004 and was primarily aimed at seeing what effect low-dose aspirin and vitamin E have on cardiovascular health and cancer risk.
At a mean follow-up period of 19 years, the data showed that 0.8% of women with LDL cholesterol levels of 70 mg/dL or lower had suffered a hemorrhagic stroke, double the rate of women with LDL cholesterol levels between 100 and 130 mg/dL. They also found women with the lowest triglyceride levels had higher rates of hemorrhagic stroke (0.6% versus 0.4% in women with higher triglycerides).
Rist told MD Magazine® that the data should be a consideration for physicians when treating women with certain risk factors for stroke.
“The main message of the paper is that although women with very low levels of LDL are usually considered to be at low risk of heart attacks and ischemic stroke, these women may have an increased risk of experiencing a hemorrhagic stroke,” she said. “Therefore, it is important to manage other risk factors for hemorrhagic stroke, such as hypertension and smoking.”
Rist said further study will be needed to determine how to lower hemorrhagic stroke risk in women with very low LDL. She also noted that while the study looked at lipid levels in general, it did not look specifically at the effects of cholesterol-lowering therapies on stroke risk.
One limitation of the study was that it only took cholesterol and triglyceride counts at the start of the study, meaning the data could not account for changes in lipid levels that occurred after enrollment in the study. Rist said investigators were also unable to determine how menopause status affects the increase in hemorrhagic stroke risk. In general, stroke risk increases in the years following menopause.
“Unfortunately, due to the low number of women who were premenopausal at baseline, we were not able to perform this type of analysis in our study,” Rist said.
The study, “Lipid levels and the risk of hemorrhagic stroke among women,” was published in Neurology.