January 20, 2010
Men and women whose cholesterol levels were mildly elevated in middle age are at increased risk of developing Alzheimer's disease as they grow old, new research shows. The findings add to a growing body of evidence that high cholesterol, a risk factor for heart disease, may also bode poorly for brain health.
Healthy total cholesterol levels are generally regarded as being at 200 or less (as measured in milligrams of cholesterol per deciliter of blood). Earlier studies have shown that middle-aged people with high cholesterol levels, generally regarded as 240 or higher, are at increased risk of Alzheimer's in old age.
This study showed that those with slightly elevated, or borderline cholesterol levels, around 220 at midlife were at increased risk of developing Alzheimer's in old age. They were also at higher risk of vascular dementia, a form of memory loss linked to damaged blood vessels in the brain, than those with healthy cholesterol levels.
In the study, researchers at Kaiser Permanente in California looked at health care records from 9,844 health care plan members over four decades. They were in their early 40s at the start of the study, from 1964 to 1973, and all were mentally alert.
By the end of the study, from 1994 to 2007, all participants were in their 60s, 70s or 80s. Nearly 600 had been diagnosed with Alzheimer's disease or vascular dementia.
The researchers found that those with high cholesterol in their 40s were more likely to have Alzheimer's in old age, a finding consistent with earlier research. But even those with mildly elevated cholesterol levels, around 220, were at increased Alzheimer's risk.
Does this mean that for those people past middle age, it's too late to lower the risk of Alzheimer's by lowering cholesterol? Probably not. Many of those with high cholesterol at midlife continue to have high cholesterol as they grow older. This persistence of high cholesterol may have been partially responsible for the elevated risk seen in this study. So, lowering cholesterol, even for seniors, is likely to be of benefit.
The findings add further impetus to the common warning that it's never too early to keep cholesterol levels in check. What's good for the heart appears to be good for the brain, and taking preventive steps early may help to lower the risk of Alzheimer's many years later.
The researchers did not study the effects of drugs like statins that lower cholesterol, and investigators continue to look at the effects of these medications on brain health and preventing Alzheimer's. In the meantime, research shows that Alzheimer's appears to be a gradual process that may take decades to develop, so keeping cholesterol levels down by eating a healthy diet is likely important for brain health.
The findings were published in the medical journal Dementia and Geriatric Cognitive Disorders.
Alina Solomon, Miia Kivipelto, Benjamin Wolozin, et al: "Midlife Serum Cholesterol and Increased Risk of Alzheimer's and Vascular Dementia Three Decades Later." Dementia and Geriatric Cognitive Disorders, August 4, 2009.