Though I am usually suspicious of the terms 'correlates with', 'associated with', and 'increases/decreases risk of' etc. because when I'm lazy in my thinking I want to read them as indicating a cause not what they really are - a possible reason for much more investigation, I refer you to the following exerpt of an article by Jenny at Diabetes Update
3. Higher Levels of Cholesterol of ALL Types Correlates with LESS Likelihood of Alzheimers. It has long been known--though doctors have been brainwashed into ignoring it--that statins can cause permanent dementia, especially in older patients. Could it be because cholesterol is protective to the brain? This study would make you wonder.
It followed 1,130 adults 65 or older in New York City with no history of dementia or cognitive impairment.
Higher levels of HDL-C (>55 mg/dL) were associated with a decreased risk of both probable and possible A[lzheimers] D[isease] and probable AD compared with lower HDL-C levels (hazard ratio, 0.4; 95% confidence interval, 0.2-0.9; P = .03 and hazard ratio, 0.4; 95% confidence interval, 0.2-0.9; P = .03). In addition, higher levels of total and non–HDL-C were associated with a decreased risk of AD in analyses adjusting for age, sex, education, ethnic group, and APOE e4 genotype.