WASHINGTON High cholesterol levels in your 40s may raise the chance of developing Alzheimer's disease decades later, according to a study underscoring the importance of health factors in middle age on risk for the brain ailment.
The study involving 9,752 people in northern California found that those with high cholesterol levels between ages 40 and 45 were about 50 percent more likely than those with low cholesterol levels to later develop Alzheimer's disease.
The findings were presented on Wednesday at a meeting of the American Academy of Neurology in Chicago.
"Alzheimer's disease does not happen overnight," Dr. Alina Solomon of the University of Kuopio in Finland, who helped lead the study, said in a telephone interview.
"Alzheimer's disease has a very long preclinical phase -- a silent phase -- when you don't see any signs of the disease, but the disease is there. The pathological changes in the brain can sometimes develop over decades."
Alzheimer's disease is the most common form of dementia among older people, and researchers have been working to understand its causes and risk factors.
The findings come just weeks after another study showed that having a big belly in middle age may greatly increase one's risk of later developing Alzheimer's disease or another form of dementia.
Rachel Whitmer of the Kaiser Permanente Division of Research in Oakland, California who led that study also was involved in the new one on cholesterol levels.
"Cholesterol is just one piece of the puzzle. There are other risk factors like hypertension and obesity. The more risk factors you have, the higher the risk gets," Solomon said.
Solomon said previous research had looked at the issue of high cholesterol levels in middle age as a risk factor for later development of dementia, but did not focus specifically on Alzheimer's disease.
The people in the new study underwent detailed health evaluations between 1964 and 1973 when they were ages 40 to 45, including blood cholesterol measurements. The researchers then looked at the cholesterol measurements of the 504 people in the study who developed Alzheimer's disease decades later.
High levels of cholesterol -- a waxy, fat-like substance that occurs naturally in the body -- in the blood can raise one's risk of heart disease. Physical inactivity, obesity and a fatty diet can contribute to high cholesterol.
"The association between cholesterol and cardiovascular disease is well known. What we know now is that minding heart health may protect your brain as well," Solomon said.
Exercise and eating more fruits and vegetables can lower cholesterol, and there are cholesterol-lowering drugs as well.
(Editing by Julie Steenhuysen and Cynthia Osterman)