A new study from China suggests that those with higher levels of LDL-C have a lower incidence of dementia. They evaluated 3,800 subjects with a mean age of 69 years, performing extensive neuropsychological and cognitive ability testing. They found that the diagnosis of dementia and cognitive impairment correlated with increasing age, decreasing education level, diagnosis of type 2 diabetes, and being an ApoE4 carrier. After controlling for all these factors, they also found that those in the highest tertile of LDL-C (>142 mg/dL or 3.7 mmol/L) had a 50% lower incidence of dementia than those in the lowest tertile (<110 mg/dL or 2.9 mmol/L).
Frontiers in Neurology: High low-density lipoprotein cholesterol inversely relates to dementia in community-dwelling older adults: The Shanghai aging study
These findings are consistent with a prior study (also observational) examining the Framingham Heart Study data that found lower risk of dementia in those over 85 years old with higher cholesterol levels.
In fairness, these studies were observational studies, so they do not prove higher LDL-C directly protected against dementia. We can hypothesize why higher levels of LDL-C are associated with lower incidence of dementia. It could be a marker of overall health or nutritional status, it could be that LDL-C directly improves the health of neurons and prevents brain atrophy, or it could be more related to lack of diabetes or ApoE4 status for which a study may not always completely control.
Even without proving causation, these studies are wonderful reminders that we can easily get caught up in one specific disease processes (i.e. cardiovascular disease) and forget about the rest of the patient. The old joke is that when the surgeon talks to the family after a complicated and risky coronary bypass surgery, he says, "The surgery was a great success. The grafts were perfect, and the anastomosis were flawless, some of the best I have ever done. I'm sorry the patient died, but the surgery was wonderful."
This is a fictional over-exaggeration, but it makes my point.
Cholesterol's effects on our health are far too intricate to simply label LDL-C as "bad" and leave it at that. Such oversimplifications harm our overall understanding and eventually harms our health.
Instead, we need to focus on the whole patient, not one specific outcome. Trials should focus on all-cause mortality and overall morbidity rather than one or two specific outcomes. It doesn't do us much good to lower heart attack risk by 0.5% over five years if we are also increasing the risk of dementia, cancer or other complications.
Thanks for reading,
Bret Scher MD FACC
My good cholesterol is very high and i m very healthy... just listened to my doc temporarily