Ask any golfer if you can have too low a golf score and he will think you’re nuts. After all, the lowest score wins in golf. Ask almost any cardiologist if you can have too low LDL cholesterol levels and you are likely to get the same perplexed look. LDL cholesterol has been dubbed “bad” cholesterol. It is perceived as the major culprit in heart disease. Because statins lower LDL cholesterol so well, they are called life savers. But what if low LDL cholesterol levels were linked to hemorrhagic or bleeding strokes? A new study confirms this possibility in women (Neurology, April 10, 2019).
Old News: Low LDL Cholesterol and Bleeding Strokes
It usually comes as a shock to patients and health professionals to learn that low cholesterol, especially low LDL cholesterol, might have some negative consequences. For decades we have been told that LDL cholesterol is our enemy. The belief is that LDL cholesterol clogs our arteries and is the primary cause of heart attacks and strokes. There was no concept of too low LDL cholesterol.
We believed the LDL cholesterol mantra for a long time. Then we talked with Walter Willett, MD, DrPH, MPH. Dr. Willett is arguably one of the world’s foremost epidemiologists and nutrition scientists. At the time we talked with him he was chairman of the Department of Nutrition at the Harvard School of Public Health. Here’s what he said about very low cholesterol levels:
“…in Japan, where cholesterol levels have been low, hemorrhagic stroke rates have been extremely high, so that total cardiovascular mortality has not been very different between the United States and Japan.”
Too Low Cholesterol?
Dr. Willett went on to add this in response to our question whether cholesterol levels could ever be too low:
“there is indeed some basis for real concern, even though it’s not been absolutely proven that cholesterol levels can be driven down too low.”
Dr. Willett really shocked us when he said that at one time there was even a public health effort to raise cholesterol levels in Japan because of a problem with bleeding strokes.
Seven years before we spoke with Dr. Willett an article was published in the journal Stroke (July, 1993).
Researchers performed autopsies on men who died in a local hospital in northeast Japan between 1966 and 1984.
“Among cases of cerebral hemorrhage [bleeding stroke], serum total cholesterol levels were even lower in men with no significant stenosis in either basal or penetrating arteries than in men with stenosis [narrowing] in either type of artery.
“The association of serum cholesterol with pathogenesis varies among stroke types. Elevated serum cholesterol levels were associated with the presence of cortical artery infarction [clot blockage], while low serum cholesterol levels were associated with cerebral hemorrhage [bleeding stroke].”
A meta-analysis involving 23 prospective studies totaling 1,430,141 participants was published in the journal Stroke (July, 2013).
“Total cholesterol level is inversely associated with risk of hemorrhagic stroke. Higher level of low-density lipoprotein cholesterol seems to be associated with lower risk of hemorrhagic stroke.”
In other words, low LDL cholesterol was associated with a higher incidence of stroke and conversely, higher levels of LDL cholesterol were linked to a lower likelihood of a bleeding stroke.
New Research Linking Low LDL Cholesterol to Bleeding Strokes:
The journal Neurology is “The most widely read and highly cited peer-reviewed neurology journal.” It is also highly respected. An intriguing study published online on April 10, 2019 raises some fascinating questions about striving to achieve low LDL cholesterol levels.
The authors reviewed data collected from the Women’s Health Study. Nearly 28,000 women were followed for almost 20 years.
Results of Low LDL Cholesterol:
What they found was that women with LDL cholesterol levels that were lower than 70 mg/dl were more than twice as likely to experience a hemorrhagic stroke as those with LDL cholesterol levels between 100 and 130. The authors acknowledge that the underlying mechanisms behind this life-threatening complication are not completely understood. They go on to say, though, that:
“…it is thought that low cholesterol may result in arterial medial layer smooth muscle cell necrosis [death] and that the impaired endothelium [the inside of blood vessels] may be more susceptible to microaneursyms, which are often found in ICH [brain hemorrhage] patients.”
What About Drugs that Lower LDL Cholesterol?
Most people cannot get their LDL cholesterol below 70 without medications. The authors note:
“The association between low LDL-C or triglyceride levels and an increased risk of hemorrhagic stroke seen in some studies led to concern that statins may increase the risk of hemorrhagic stroke events. Two large meta-analyses, one only of randomized controlled trials and one of both trials and observational studies, concluded that there was no association between statin use and the risk of ICH [intracerebral hemorrhage or bleeding stroke].”
They go on to note, however:
“The differences between the statin trials and observational studies such as the one presented here may be due to the different questions the studies address. Statin trials are typically only a few years in duration and examine the effect of a pharmaceutical agent that lowers cholesterol on hemorrhagic stroke risk. In contrast, our observational study may reflect the effect of longer-term exposure to very low LDL-C levels (in the absence of cholesterol- lowering treatment) on vessel wall integrity.”
Are Your Concerned About Too Low Cholesterol?
We think of cholesterol a bit like the porridge in the story of Goldilocks and the Three Bears. If you remember this tale, our young lady did not like her porridge too cold or too hot. She preferred porridge that was “just right.” So too cholesterol may need to be neither too low nor too high. The authors noted that high levels of LDL cholesterol (above 160) seemed to be associated with an increased risk of bleeding stroke too, though the results were not statistically significant.
If you would like to read other articles we have written about the complicated issue of too low cholesterol, we invite you to go to these links:
What do you think about low LDL Cholesterol? Please share your story or thoughts in the comment section below.