Lower levels of “bad” LDL cholesterol could mean a lower risk of dementia and Alzheimer’s disease, a new study says.
People with low-density lipoprotein (LDL) cholesterol levels lower than 70 mg/dl had a 26% lower risk of dementia and 28% lower risk of Alzheimer’s, compared to people with LDL levels above 130 mg/dl, researchers reported April 1 in the Journal of Neurology, Neurosurgery & Psychiatry.
Statins taken to lower cholesterol also appeared to confer additional protection against dementia and Alzheimer’s.
“These findings emphasize the importance of achieving specific LDL cholesterol thresholds for dementia prevention,” concluded the research team led by Dr. Yerim Kim, an assistant professor of neurology with the Hallym University College of Medicine in Seoul, South Korea.
“Furthermore, it suggests a potential synergistic benefit of statin use within this optimal range,” researchers added.
Current LDL cholesterol guidelines call for lower than 100 mg/dl in healthy people, and 70 mg/dl or lower in people with a history of heart attack or stroke, according to the American Heart Association (AHA).
Those guidelines are based on a clear link between “bad” cholesterol levels and heart risk, but there’s been conflicting evidence regarding the association between LDL cholesterol and brain health, researchers said in background notes.
Early studies suggested that lowering LDL cholesterol through statin use might cause some cognitive impairment, but later data has shown that low LDL does not increase the risk of dementia, researchers said.
However, it’s not been clear whether lowering LDL cholesterol might actually protect the brain, researchers said.
To look into this, researchers analyzed data from 11 South Korean university hospitals on more than 192,000 people with LDL levels lower than 70 mg/dl and 379,000 patients with LDL levels higher than 130 mg/dl.
The team created nearly 109,000 matched pairs from that data, lining up people with low cholesterol against similar folks with high cholesterol.
Analysis showed that the people with low LDL cholesterol had a lower risk of both dementia and Alzheimer’s.
Further, people using statins to achieve low LDL levels had a 13% lower risk of dementia and 12% lower risk of Alzheimer’s compared to people with low levels who weren’t taking statins, results show.
“Statin use contributes additional protection against dementia in individuals with LDL cholesterol levels below 70 mg/d,” the team wrote.
However, the protective effect from low LDL cholesterol diminished as levels declined, and eventually disappeared among people whose LDL levels were lower than 30 mg/dl.
“The primary findings of this study highlight the critical importance of LDL cholesterol levels in dementia risk, emphasizing the critical importance of these levels irrespective of statin use,” researchers concluded. “Lower LDL cholesterol levels are directly associated with reduced dementia incidence, supporting cholesterol management as fundamental in preventing dementia.”
The research team also speculated that LDL cholesterol might influence dementia risk by affecting cholesterol levels in the brain, promoting inflammation and oxidative stress, or by clogging the arteries that supply blood to the brain.
Statins might enhance these effects by reducing brain inflammation and regulating the metabolism of amyloid beta, a brain protein linked to Alzheimer’s, researchers added.
However, researchers noted that the study can’t prove a cause-and-effect relationship between LDL cholesterol and dementia. Clinical trials will be needed to prove a direct link.