Low cholesterol levels are associated with a higher risk of Alzheimer's

This study was published in the Archives of Neurology 2004 May;61(5):705-14

Study title and authors:
Relation of plasma lipids to Alzheimer disease and vascular dementia.

Reitz C, Tang MX, Luchsinger J, Mayeux R.
Gertrude H. Sergievsky Center, Columbia University College of Physicians and Surgeons, New York, NY, USA.

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/15148148

This study investigated the relationship between cholesterol levels and Alzheimer disease and vascular dementia. (Vascular dementia is caused by problems in the supply of blood to the brain usually from a stroke). The study included 4,316 participants aged 65 years and older.

The study found:
(a) The risk of prevalent Alzheimer's was 28% higher in those who had low cholesterol, under 172 mg/gL (4.4 mmol/L), compared to those with cholesterol levels between 197-225 mg/dL (5.1-5.8 mmol/L).
(b) The risk of prevalent Alzheimer's was 34% higher in those who had low levels of high density lipoprotein (HDL) cholesterol, under 37 mg/gL (.95 mmol/L), compared to those with high density lipoprotein (HDL) cholesterol levels over 55 mg/dL (1.4 mmol/L).
(c) The risk of prevalent vascular dementia was 20% higher in those who had low cholesterol, under 172 mg/gL (4.4 mmol/L), compared to those with cholesterol levels between 197-225 mg/dL (5.1-5.8 mmol/L).
(d) The risk of prevalent vascular dementia was 40% higher in those who had low levels of high density lipoprotein (HDL) cholesterol, under 37 mg/gL (.95 mmol/L), compared to those with high density lipoprotein (HDL) cholesterol levels over 55 mg/dL (1.4 mmol/L).

The data from the study reveals that low cholesterol levels are associated with a higher risk of Alzheimer's.