What's more important, an analysis of vascular risk factors showed that participants who had diabetes or high blood pressure, also called hypertension, had a higher chance of developing dementia.

In fact, diabetes was almost as strong a predictor of dementia as the presence of the APOE4 gene.

The researchers also found a link between dementia and prehypertension, a condition in which blood pressure levels are higher than normal but lower than hypertension.

And race did not influence the association between dementia and the vascular risk factors they identified, according to the study.

In addition, smoking cigarettes exclusively increased the chances of dementia for whites but not blacks.

"Our results contribute to a growing body of evidence linking midlife vascular health to dementia," said Gottesman. "These are modifiable risk factors. Our hope is that by addressing these types of factors early, people can reduce the chances that they will suffer from dementia later in life."