Background The link between low-density lipoprotein cholesterol (LDL-C) levels and dementia risk is poorly understood, with conflicting evidence on the role of LDL-C and the impact of statin therapy on cognitive outcomes. Thus, we aimed to examine the association between low-density LDL-C levels and the risk of dementia and assess the influence of statin therapy.

Methods We retrospectively analysed data from 11 university hospitals participating in the Observational Medical Outcomes Partnership (OMOP) Common Data Model (CDM). Participants with a prior diagnosis of dementia or those with <180 days of observation before cohort inclusion, and those included in both cohorts were excluded. The primary outcome was all-cause dementia, with the secondary outcome being Alzheimer’s disease-related dementia (ADRD). The study utilised 1:1 propensity score matching to compare individuals with LDL-C levels below 70 mg/dL (1.8 mmol/L) against those with levels above 130 mg/dL (3.4 mmol/L), resulting in a primary analysis cohort of 108 980 matched patients. Secondary analyses further examined LDL-C thresholds below 55 mg/dL (1.4 mmol/L) and the influence of statin use.

Results The LDL-C levels below 70 mg/dL (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 ADRD, compared with levels above 130 mg/dL (3.4 mmol/L). For LDL-C levels below 55 mg/dL (1.4 mmol/L), there was an 18% risk reduction for both outcomes. Among those with LDL-C <70 mg/dL (<1.8 mmol/L), statin use was associated with a 13% reduction in all-cause dementia risk and a 12% decrease in ADRD risk compared with non-users.

Conclusion Low LDL-C levels (<70 mg/dL (<1.8 mmol/L)) are significantly associated with a reduced risk of dementia, including ADRD, with statin therapy providing additional protective effects. These findings support the necessity of targeted lipid management as a preventive strategy against dementia, indicating the importance of personalised treatment approaches.