Low levels of ‘bad cholesterol’ may actually increase stroke risk
Women with low LDL cholesterol levels may be more at risk of bleeding stroke, new research finds.
According to the latest guidelines from the American College of Cardiology and the American Heart Association, a person’s levels of low-density lipoprotein (LDL) cholesterol should remain under 100 milligrams per deciliter (mg/dl) to maintain health.
That is because, generally, specialists have considered LDL to be “bad” cholesterol. LDL carries cholesterol to the cells that need to make use of it, but if its levels are too high, it can stick to the arteries, leading to all manner of cardiovascular problems.
However, new research from the Brigham and Women’s Hospital and Harvard Medical School in Boston, MA, has found that women with LDL levels below 100 mg/dl may actually be more at risk of hemorrhagic (bleeding) stroke. This type of stroke, though less common than an ischemic stroke, is harder to treat and thus more dangerous to the person experiencing it.
“Strategies to lower cholesterol and triglyceride levels, like modifying diet or taking statins, are widely used to prevent cardiovascular disease,” explains study author Pamela Rist, from Brigham and Women’s Hospital.
“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 new study’s findings now appear online ahead of print in the journal Neurology.
Low LDL levels more than double risk
In this study, the researchers looked at the data of 27,937 women aged 45 years and over who took part in the Women’s Health Study. The data included measurements of each participant’s LDL cholesterol, high-density lipoprotein (HDL) cholesterol, and triglyceride levels at the beginning of the study.
Rist and team looked at both these data and the participants’ medical records over an average 19-year follow-up period.
They found that during this time, 137 women had experienced a bleeding stroke. They noted that nine (or 0.8 percent) of the 1,069 women with LDL levels of 70 mg/dl or lower experienced this type of cardiovascular event, whereas it affected 40 (or 0.4 percent) of the 10,067 women with LDL cholesterol levels of 100–130 mg/dl.
After adjusting for possible confounding factors, the researchers concluded that women with the lowest levels of LDL cholesterol were more than twice (2.2 times) as likely to have a bleeding stroke as those with high LDL cholesterol levels.
They identified a similar association in relation to triglyceride levels: 34 (or 0.6 percent) of the 5,714 women with the lowest triglyceride levels had experienced a bleeding stroke, whereas this event had occurred in 29 (0.4 percent) of the 7,989 women with the highest triglyceride levels.
Once more, after adjusting for other potential risk factors, the team concluded that women with the lowest triglyceride levels had a risk of bleeding stroke that was twice as high as that of the women with the highest triglyceride levels.
At the same time, the researchers found no such discrepancies regarding total cholesterol and HDL cholesterol levels.
“Women with very low LDL cholesterol or low triglycerides should be monitored by their doctors for other stroke risk factors that can be modified, like high blood pressure and smoking, in order to reduce their risk of hemorrhagic stroke,” Rist advises.
“Also, additional research is needed to determine how to lower the risk of hemorrhagic stroke in women with very low LDL and low triglycerides,” she adds.
The researchers also admit that their study has faced some limitations, including the fact that they only had access to cholesterol and triglyceride level measurements at baseline and that they did not have a chance to investigate whether menopause-related factors played a role in some of the women’s increased stroke risk.