That nugget comes from researchers at the Columbia University College of Physicians and Surgeons in New York. They recruited 1,130 senior citizens from Manhattan (all of them age 65 or older) and took baseline measurements of their cholesterol levels and their neurological states. They also checked to see whether these seniors had a particular mutation in the APOE gene that could increase their risk of developing Alzheimer’s.
They tracked each volunteer for more than four years, on average. During that time, 89 of the seniors were diagnosed as having “probable” Alzheimer’s and another 12 had “possible” Alzheimer’s. Compared to those with the lowest levels of high-density lipoprotein – the good cholesterol commonly known as HDL – volunteers with the highest levels were 60% less likely to be told they had a probable or possible case of Alzheimer’s.
To make it into the “high HDL” category, volunteers had to have more than 56 milligrams of HDL per deciliter of blood. Those in the lowest HDL category had no more than 38 mg per dL of blood. In their analysis, the researchers controlled for the age, gender, body-mass index, education and ethnic groups of the volunteers, along with the type of APOE genes they had and other health conditions like heart disease and type 2 diabetes.