Relation between cholesterol levels,statins and Alzheimer's disease in the human population

This review paper discusses potential relationships between Cholesterol levels, the therapeutic use of Statins and the risk of Alzheimer s Disease. Comparisons have also been made between the Western populations and Oriental populations. Epidemiological studies have shown that statins, which reduce the levels of plasma cholesterol by inhibiting the enzyme 3 hydroxy-3methylglutaryl-coenzyme A (HMGCoA) reductase, reduce the risk of Alzheimer s disease by up to 70%. Further research is required to determine whether cholesterol levels have a direct, causative, or indirect relationship with Alzheimer disease. Also, it is not clear why some statins reduce the prevalence of AD and others do not. Statins may have an affect on other AD risk factors, or act by mechanisms which are independent of their effects on cholesterol levels?