The chance of developing dementia is tied to a number of factors, including some that can also influence cardiovascular health, such as diabetes, high blood pressure, and smoking. A new study shows that having these risk factors in middle age might increase the likelihood of having dementia later in life.

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The results of a recent study have shown that avoiding certain modifiable risk factors in middle age can reduce a person's likelihood of developing dementia later in life.

A report on the study, which was led by Rebecca Gottesman, a professor of neurology at Johns Hopkins University in Baltimore, MD, is published in JAMA Neurology.

"This study supports the importance of controlling vascular risk factors like high blood pressure early in life in an effort to prevent dementia as we age," says Dr. Walter J. Koroshetz, director of the National Institute of Neurological Disorders and Stroke, which is part of the National Institutes of Health (NIH).

"What's good for the heart is good for the brain," says Dr. Koroshetz, commenting that as the population ages, dementia is becoming an increasing public health concern in the United States.

Dementia is an umbrella term for a group of terminal conditions that progressively diminish brain function. Symptoms include increasing memory loss, confusion, and difficulties with speaking and understanding.

Alzheimer's disease is the most common type of dementia, accounting for nearly two thirds of cases. Other types include vascular dementia and mixed dementia.

A growing public health concern

There are more than 5 million people living with Alzheimer's disease in the U.S., and this figure is expected to rise to 16 million by 2050. Alzheimer's is the sixth leading cause of death among all U.S. adults and the fifth leading cause among seniors.

Since 2000, deaths to Alzheimer's disease in the U.S. have risen by 89 percent. In contrast, deaths to heart disease have fallen by 14 percent.

For their study, Prof. Gottesman and colleagues analyzed data from 15,744 participants of the Atherosclerosis Risk in Communities (ARIC) study.

The participants, 73 percent of whom were white and 27 percent of whom were black, were aged 45 to 64 years when they were recruited between 1987 and 1989, and they underwent medical exams at clinics in four different states.

Over an average follow-up period of 23 years, the participants underwent four more medical exams. Apart from the first and third time, the exams included tests of memory and thinking.

During the follow-up, 1,516 participants were diagnosed with dementia, and 57 percent of them were female and 35 percent were black.

Diabetes as strong as genetic risk

When they analyzed the participant data in relation to dementia incidence, the researchers found that age was the strongest risk factor for dementia, followed by being a carrier of APOE4, which is "the primary known genetic risk factor" for Alzheimer's disease.

Black people were also found to be at higher risk for dementia, as were participants who had spent fewer years in full-time education and had not graduated from high school.

In addition to these non-modifiable risk factors, the researchers found that a number of modifiable cardiovascular risk factors in mid-life were linked to a raised risk of dementia - namely, being a smoker, having high blood pressure, and having diabetes.

Having diabetes was found to be almost as strong a risk factor as carrying the Alzheimer's-related APOE4 gene.

The researchers also found that raised risk of dementia was linked to prehypertension, a condition in which blood pressure is not high enough to be classed as hypertension but is quite close.

Raised levels of Alzheimer's brain protein

Finally, the team found that race did not affect the link between raised dementia risk and diabetes, hypertension, or prehypertension. Being a smoker in mid-life, however, appeared only to be a higher risk for dementia in white people; no such link was found for black people.

In further analysis, the team eliminated the possibility that having had a stroke might explain the link between these cardiovascular risk factors and dementia. This showed that smoking and having diabetes, hypertension, or prehypertension in mid-life conferred the same higher risk of dementia in stroke-free and stroke-affected participants alike.

In another study, Prof. Gottesman's team analyzed brain scans from ARIC participants who were dementia-free on enrolment. They found that those who had one or more of the cardiovascular risk factors in mid-life were more likely to have higher brain levels of an Alzheimer's-related protein called beta amyloid.

This link was independent of the presence of the APOE4 gene and of risk factors that developed later: higher levels of beta amyloid were no more likely among participants who developed the cardiovascular risk factors after the age of 65.

"Our results contribute to a growing body of evidence linking mid-life vascular health to dementia. 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."

Prof. Rebecca Gottesman

The researchers note that while their study establishes links between these mid-life modifiable vascular risk factors and dementia later on, it will be up to further studies to find out if controlling them actually reduces the incidence of dementia.

The NIH Mind Your Risks public health campaign aims to help people reduce their risk for stroke, heart disease, and dementia with advice on how to lower blood pressure, give up smoking, eat more healthfully, and keep active.