Lowering low-density lipoprotein (LDL) cholesterol reduces the risk of heart attacks and stroke, with an ideal value below 100 milligrams per deciliter (mg/dL). But can it be too low? A new study finds that women who have levels of LDL cholesterol 70 mg/dL or lower may be more than twice as likely to have a hemorrhagic stroke than women with LDL cholesterol levels from 100 to 130 mg/dL.

LDL cholesterol is called bad cholesterol because it can lead to fatty build-up in the arteries. The study also found that women with the lowest triglyceride levels, a fat found in the blood, had an increased risk of hemorrhagic stroke compared to those with the highest triglyceride levels.

Hemorrhagic strokes, also known as bleeding strokes, are much less common than ischemic strokes, when blood flow is blocked to the brain. They are also more difficult to treat and therefore more likely to be deadly.

«Strategies to lower cholesterol and triglyceride levels, like modifying diet or taking statins, are widely used to prevent cardiovascular disease,» said study author Pamela Rist, ScD, of Brigham and Women’s Hospital in Boston and a member of the American Academy of Neurology. «But our large study shows that in women, very low levels may also carry some risks. Women already have a higher risk of stroke than men, in part because they live longer, so clearly defining ways to reduce their risk is important.»

The study involved 27,937 women age 45 and older enrolled in the Women’s Health Study who had total cholesterol, LDL cholesterol, high density lipoprotein (HDL) cholesterol, which is known as good cholesterol, and triglycerides measured at the start of the study. Researchers then reviewed medical records to determine how many women had a bleeding stroke.

With an average of 19 years of follow-up, researchers identified 137 women who had a bleeding stroke.

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Materials provided by American Academy of Neurology. Note: Content may be edited for style and length.