Low ‘bad’ cholesterol levels may mean lower dementia risk

By Stephen Beech

People with low levels of "bad" cholesterol are less likely to develop dementia, according to new research.

And statins lowered the risk of the debilitating condition even further in people with low LDL - or "bad" cholesterol - levels, say scientists.

LDL - or "low-density lipoprotein" - cholesterol is often called the “bad” cholesterol because it collects in the walls of blood vessels, raising of potentially deadly health issues such as a heart attack or stroke.

Most of the cholesterol in the human body is LDL. The rest is high-density lipoprotein (HDL) or “good” cholesterol.

HDL takes LDL to the liver, where it’s flushed out of the body.

The new study, published in the Journal  of Neurology Neurosurgery & Psychiatry, shows that people with low levels of LDL cholesterol (LDL-C) in their blood have a lower risk of dementia, including a lower risk of Alzheimer’s disease-related dementia.

The use of statins conveyed an additional protective effect for people with low LDL-C, according to the research, specifically those with blood levels less than 1.8 mmol/L (<70 mg/dL), reducing their risk of dementia even further.

But reducing LDL-C to "very low" levels below 0.8 mmol/L (<30mg/dL) did not reduce dementia risk further.

Study author Dr. Minwoo Lee, of Hallym University College of Medicine, South Korea, said: "The benefits of low LDL-C levels to protect against cardiovascular events is well recognized, but the relationship between LDL-C levels and dementia has been less clear, particularly the cut-off for LDL-C below which there is no further benefit for reducing the risk of cognitive decline."

The research accessed data collected by 11 university hospitals on adult outpatients with no previous diagnosis of dementia followed for at least 180 days after LDL-C testing.

The researchers identified 192,213 people with LDL-C levels less than 1.8 mmol/L and 379,006 patients with LDL-C levels more than 3.4 mmol/L and matched people in each group into 108,980 matched pairs.

Analysis of subsequent diagnoses of dementia showed that LDL-C levels below 1.8 mmol/L were associated with a 26% reduction in the risk of all-cause dementia and a 28% reduction in the risk of Alzheimer’s disease-related dementia, compared with LDL-C levels above 3.4 mmol/L.

Dr. Lee said: "The protective effect against cognitive decline lessened at lower LDL-C levels and eventually disappeared entirely.

"At LDL-C levels below 1.4 mmol/L, there was an 18% risk reduction for both all-cause dementia and Alzheimer’s disease-related dementia compared with LDL-C levels above 3.4 mmol/L, and when LDL-C levels fell below 0.8 mmol/L the risk reductions disappeared.

"Statin use conferred additional protection against dementia in the presence of low LDL-C levels.

"Among people with LDL-C levels below 1.8 mmol/L, statin use was associated with a 13% reduction in all-cause dementia risk and a 12% decrease in risk of Alzheimer’s disease-related dementia compared with non-users."

The researchers emphasized that it was an observational study, so no firm conclusions can be drawn about cause and effect.

But Dr. Lee said: “Low LDL-C levels are significantly associated with a reduced risk of dementia, including Alzheimer’s disease-related dementia, with statin therapy providing additional protective effects.”

He added: “These findings underscore the crucial role of managing LDL-C in lowering dementia risk.”