Paradoxically, a Mendelian randomisation study involving 111,194 individuals from two prospective general populations reported that a low LDL-c level due to genetic variation in PCSK9 and HMGCR is associated with a high risk of neurocognitive diseases including Alzheimer’s disease and Parkinson’s disease32. This evidence concerns the gene HMGCR and early-onset autosomal dominant Alzheimer disease.