Medical care to optimize vascular health may be the best preventive for mixed dementia (Alzheimer’s disease combined with vascular dementia), which accounts for up to 20 percent of dementia cases, especially older patients, according to an article in the December 15th issue of the Journal of the American Medical Association.

Dementia experts have concluded that many people with symptoms attributed solely to Alzheimer’s - memory loss, confusion, wandering, trouble following instructions - may in fact have mixed dementia.

“Having risk factors like high blood pressure and high cholesterol does damage to small blood vessels in the brain and can cause death of brain cells over time,” said lead author Kenneth Langa, MD, PhD. “In addition, the Alzheimer’s disease process itself can affect the walls of blood vessels in the brain, making strokes more likely. Strokes can cause dementia through the death of large areas of brain tissue, or through the build-up of damage from multiple small strokes caused by atherosclerosis in small arteries in the brain or the larger carotid arteries in the neck.”

In the current work, researchers reviewed all recent medical studies on mixed dementia, vascular dementia, and Alzheimer’s disease. They analyzed hundreds of articles, noting any results from drug studies that were relevant to mixed dementia.

The review shows that drugs designed to slow the progression of Alzheimer’s disease have about the same effect in people with mixed dementia as in people with Alzheimer’s alone. That is, in some people the drugs produce a measurable but not dramatic improvement on tests of cognitive function or other measures, or slightly slow an inevitable decline. The authors looked at drugs like galantamine, rivastigmine, donepezil, and memantine.

However, when the authors reviewed the evidence relating to cardiovascular-protective therapy and dementia, they found significant benefits. They concluded that efforts to treat cardiovascular risk factors, especially high blood pressure, may be more effective than memory drugs in protecting brain function.

Still, the authors noted that more studies are needed to give doctors a full picture of mixed dementia, and to show them what works, and what doesn’t, in preventing and slowing it.

“Until those studies are completed, physicians should talk with each patient or family individually about the treatment route to pursue,” said Langa. That discussion, in all patients with dementia that might have a cardiovascular component, should include advice about lifestyle changes and treatments to address risk factors such as high blood pressure, high cholesterol, diabetes, and physical inactivity. In patients with arrhythmias, carotid stenosis, or clotting disorders that can greatly increase the risk of stroke, further treatment may be needed.

If a decision is made to prescribe one of the new Alzheimer’s drugs, the authors recommend that doctors follow up with patients or their families in two to three months to see if there has been any improvement in memory or behavior, or whether the patient’s cognitive decline has slowed.

The new review focuses on findings from randomized controlled drug trials, and observational studies based on trends among specific populations. Taken together, the analysis suggests that the cardiovascular system may have a lot more to do with mental function than many people realize. Paying attention to cardiovascular risk factors could prevent some dementia and decrease the added burden of strokes in those with Alzheimer’s disease.

For example, one study showed a 50 percent reduction in the incidence of dementia in a group of patients with high blood pressure who were treated over four years with a calcium-channel blocking blood pressure drug. And patients who received the blood pressure drug had a lower chance of developing Alzheimer’s disease, vascular dementia or mixed dementia.

This corresponds with observational data showing that people with high blood pressure are more likely to develop cognitive impairment, a mild form of dementia that often acts as a warning sign for later dementia. And other observational studies have suggested that treatment for high blood pressure can protect against cognitive decline.

The authors also looked at evidence relating to drugs that reduce cholesterol or thin the blood. To date, they find, prospective studies on cholesterol drugs called statins haven’t shown a specific effect on dementia, but follow-up periods in such studies have been short.

A recent study led by the new paper’s senior author, Eric Larson, M.D., MPH, notes that people who have a certain genetic characteristic that puts them at higher risk for both heart disease and dementia may get more cognitive benefit than others from statin therapy. In an observational study, his team found that people with a specific genetic variation that alters production of a protein called APOE received more cognitive benefit from statins than others.