People with low levels of low-density lipoprotein cholesterol (LDL-C) in their blood have a lower risk of dementia, including a lower risk of dementia related to Alzheimer’s disease, shows a study published online in The Journal of Neurology Neurosurgery and Psychiatry .
Statin use provided an additional protective effect for people with low LDL-C, specifically those with blood levels below 1.8 mmol/L (<70 mg/dL), further reducing the risk of dementia.
However, lowering LDL-C to very low levels below 0.8 mmol/L (<30mg/dL) did not further reduce the risk of dementia.
The benefits of low LDL-C levels to protect against cardiovascular events are well recognized, but the relationship between LDL-C levels and dementia has been less clear, particularly the cutoff for LDL-C below which there is no longer benefit in reducing the risk of cognitive decline.
To address this, the authors accessed data collected by 11 university hospitals on adult outpatients with no prior diagnosis of dementia who were followed for at least 180 days after LDL-C testing. They identified 192,213 people with LDL-C levels less than 1.8 mmol/L (<70 mg/dL) and 379,006 patients with LDL-C levels more than 3.4 mmol/L (>130 mg/dL) and matched individuals in each group into 108,980 pairs.
Analysis of subsequent dementia diagnoses showed that LDL-C levels below 1.8 mmol/L (<70 mg/dL) were associated with a 26% reduction in the risk of all-cause dementia and a 28% reduction in the risk of Alzheimer’s-related dementia, compared with LDL-C levels above 3.4 mmol/L (LDLM.
The protective effect against cognitive decline diminished at lower LDL-C levels and eventually disappeared completely. At LDL-C levels below 1.4 mmol/L (<55mg/dL), 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 (>130mg/dL), and when LDL-C levels fell below 0.8 mmol/L (<30mg/dL) 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 (<70 mg/dL), statin use was associated with a 13% reduced risk of all-cause dementia and a 12% reduced risk of Alzheimer’s disease-related dementia compared with nonusers.
This is an observational study and as such, firm conclusions about cause and effect cannot be drawn. The authors also acknowledge that the study has some limitations, including the potential for unmeasured confounders due to its retrospective design, possible underreporting of dementia cases due to variations in diagnostic accuracy between hospitals, and the focus on baseline LDL-C levels when lipid profiles can change over time.
However, the authors conclude: “low LDL-C levels (<70 mg/dL (<1.8 mmol/L)) are significantly associated with a reduced risk of dementia, including Alzheimer’s disease-related dementia, with statin therapy providing additional protective effects.”
They add: “These findings emphasize the crucial role of managing LDL-C in reducing dementia risk.”
Provided by British Medical Journal
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