However, eating a low-fat diet and keeping your cholesterol down doesn't seem to help matters, a new Dutch study says.
Researchers followed 5,395 men and women with a mean age of 68 for six years, analyzing their intake of dietary fat and their blood cholesterol levels. Over the course of the study, 197 people developed dementia.
The study found no link between high-fat diets or elevated cholesterol and the development of dementia.
However, researchers caution that more research needs to be done to confirm the findings.
"We think it is premature to conclude from our observational study that cholesterol or cholesterol-affecting fats are not associated with risk of dementia," write the authors from the Erasmus Medical Center in Rotterdam, The Netherlands. "Larger, prospective studies with longer follow-up periods are needed to confirm our findings."
The study appears in tomorrow's issue of Neurology.
Researchers studied two types of dementia: Alzheimer's disease and vascular dementia. In the study, 146 developed Alzheimer's disease and 29developed vascular dementia, which is usually caused by multiple small strokes in the brain.
The precise cause of Alzheimer's is unknown. However, a hallmark of the progressive disease is the excessive formation of amyloid plaques, clumps of protein fragments that accumulate around the neurons in the brain.
About 4 million Americans have Alzheimer's disease, making it the most common form of dementia in the elderly, according to the Alzheimer's Association.
Previous research has shown that cholesterol-lowering drugs called statins lower the risk of developing dementia, says Dr. Irene Litvan, director of the movement disorders program at the University of Louisville School of Medicine.
Research has also indicated that dietary fat and high cholesterol could contribute to the formation of amyloid proteins.
In their analysis of dietary intake of fat, researchers looked at several types of fat, including trans fats -- which are thought to be particularly bad for the cardiovascular system -- and polyunsaturated fatty acids, which research has shown has anti-inflammatory properties and may protect against some diseases. Polyunsaturated fats are those found in olive oil and fatty fish such as salmon.
No kind of fat had any effect on the development of dementia, according to the study.
Litvan says it's far too soon to heap on the mashed potatoes and gravy with abandon.
"It's a good study, but it's a small study," she says. "The number of people who actually develop the disease is not huge. You never have a definitive answer unless you have a large number of patients participating or a large number who develop the disease."
And high cholesterol and a fatty diet have been shown to contribute to another major killer: cardiovascular disease.
"I maybe wouldn't watch my intake of fats to prevent dementia, but I would watch it for this reason," Litvan says.
What To Do
For more information about Alzheimer's disease, check out the Alzheimer's Association. The National Institute of Neurological Disorders and Stroke has more information about vascular dementia.