Although the findings stop short of directly proving that high cholesterol causes Alzheimer's disease or that lowering it would reduce the risk.

"We found that high cholesterol levels were significantly related to brain plaques associated with Alzheimer's disease," said study author Kensuke Sasaki, MD, PhD, of Kyushu University in Fukuoka, Japan.

The researchers looked at the brains of 147 people (76 men, 71 women) who were residents of a Japanese town and alive in 1988 when they underwent clinical examinations.

All of the participants died between 1998 and 2003.

About a third of them had been diagnosed with dementia during life.

When compared to people with low cholesterol levels, those with high cholesterol levels were more likely to have the bits of protein known as plaques: 62 percent versus 86 percent, respectively.

The study found no link between high cholesterol and the tangles that develop in the brain with Alzheimer's disease.

In addition to high cholesterol increasing the risk of Alzheimer's disease, Sasaki previously found that insulin resistance, a sign of diabetes, may be another risk factor for brain plaques associated with Alzheimer’s disease.

"Our study clearly makes the point that high cholesterol may contribute directly or indirectly to plaques in the brain," Sasaki said, "but failed treatment trials of cholesterol-lowering drugs in Alzheimer's disease means there is no simple link between lowering cholesterol and preventing Alzheimer's."