Yahoo Lifestyle Lowering This Type of Cholesterol May Cut Your Dementia Risk by 26%
You can't really argue with the fact that high cholesterol is bad for your heart. There is plenty of scientific evidence showing that “bad” cholesterol, also known as low-density lipoprotein (LDL-C), raises your risk of heart disease. But when it comes to how cholesterol affects other conditions, like dementia, the science has been a lot less clear—and sometimes downright contradictory.
One study, for example, found that people with high LDL-C levels had an increased risk of dementia. But it also found that having low LDL-C levels raised the risk in people who weren’t taking statins. And then there are those who argue that lowering cholesterol has nothing to do with dementia or cognitive decline at all.
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So what’s going on here? A new study published this week in the Journal of Neurology Neurosurgery & Psychiatry may finally help clear up the confusion.
Related: Stop This Habit By 50 to Avoid High Cholesterol
How Cholesterol Affects the Brain
According to the study, people with low LDL-C levels actually have a lower risk of dementia, which includes Alzheimer’s disease. Taking statins with low LDL-C levels also conferred a more protective effect, further reducing their risk of dementia.
As for how they defined “low,” the researchers found a reduced dementia risk when LDL cholesterol levels were under 1.8 mmol/L (that’s less than 70 mg/dL). For context, the American Heart Association considers anything under 100 mg/dL to be heart-healthy, as it helps reduce plaque buildup and lowers the risk of heart disease and stroke.
Scientists aren’t exactly sure how cholesterol affects the brain, but they do have some theories. One is that high cholesterol levels in the brain may contribute to the buildup of amyloid and tau, two proteins strongly linked to Alzheimer’s disease. Thus, by reducing unhealthy cholesterol levels, it could help slow the accumulation of these proteins.
Another is that high LDL cholesterol may raise dementia risk indirectly, by increasing the likelihood of stroke. Strokes cut off blood flow to the brain, damaging brain cells the longer they’re deprived of oxygen and glucose. And the effects can be long-lasting: Research suggests that about 25% of people who’ve had a stroke go on to develop cognitive impairments, most commonly vascular dementia.
Still, there are lingering questions about whether blood cholesterol levels affect the brain at all—especially since the brain actually produces its own cholesterol, separate from the rest of the body. That’s where this new study adds valuable insight.
Related: The Mini Stroke Symptom Most People Miss
What Did the Study Find?
For the study, researchers analyzed health data from outpatient adults who had previously been diagnosed with dementia and received LDL-C testing across 11 different hospitals. Each person's health was tracked for at least 180 days. In total, they identified 192,213 people with low LDL cholesterol levels and 379,006 with high LDL cholesterol levels (defined as over 130 mg/dL).
After 180 days, the results were clear: People with low LDL cholesterol levels (<70 mg/dL) had a 26% lower risk of all-cause dementia and a 28% lower risk of Alzheimer’s disease compared to those with high LDL cholesterol.
Related: Why High Cholesterol Isn't Always Bad, Cardiologists Explain
Ideal Cholesterol Numbers to Protect Against Dementia
Does that mean the lower your LDL cholesterol, the lower your risk of dementia? Not exactly.
While the researchers did observe that LDL levels below 70 mg/dL were associated with a reduced risk, that protective effect started to taper off when levels dipped too low. Specifically, people with LDL cholesterol below 55 mg/dL saw only an 18% reduction in risk for both dementia and Alzheimer’s. Further, when levels dropped below 30 mg/dL, the protective effects disappeared altogether.
Interestingly, statin use made a difference too. Among people with low LDL levels (<70 mg/dL), those who took statins had an additional 13% lower risk of developing dementia and a 12% lower risk of Alzheimer’s compared to those who had low cholesterol but didn’t take statins.
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Sources
"Association between cholesterol levels and dementia risk according to the presence of diabetes and statin use: a nationwide cohort study." Scientific Reports.
"LDL Cholesterol Lowering: Is There a Risk for Dementia and Hemorrhagic Stroke?" American College of Cardiology.
"Low-density lipoprotein cholesterol levels and risk of incident dementia: a distributed network analysis using common data models." Journal of Neurology Neurosurgery & Psychiatry.
"What Your Cholesterol Levels Mean." American Heart Association.
"Cholesterol And Dementia Risk." Alzheimer’s Research UK.
"Stroke injury, cognitive impairment and vascular dementia." Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease.
