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Dementia Risk Factors Explained

The risk of Alzheimer's disease, vascular dementia, and several other dementias goes up significantly with advancing age.
Genetics/Family History
Researchers have discovered a number of genes that increase a person's risk of developing Alzheimer's disease. Although people with a family history of Alzheimer's disease are generally considered to be at heightened risk of developing the disease themselves, many people with a family history of the condition never develop the disease, and many without a family history of Alzheimer's disease do get the disease. In most cases, it is still impossible to determine a specific person's risk for Alzheimer's disease based on family history alone.
Some families with Creutzfeldt-Jakob disease, Gerstmann-Straüssler-Scheinker syndrome (GSS), or fatal familial insomnia have mutations in the prion protein gene. However, these disorders can also occur in people without the gene mutation. Individuals with these mutations are at significantly higher risk of developing these forms of dementia. Abnormal genes are also clearly implicated as risk factors for dementia associated with Huntington's disease, frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), and several other kinds of dementia.
Down Syndrome
Studies have found that most people with Down syndrome develop characteristic Alzheimer's disease plaques and neurofibrillary tangles by the time they reach middle age. Many of these individuals also develop symptoms of dementia.
Mild Cognitive Impairment
While not all people with mild cognitive impairment develop dementia, people with this condition do have a significantly increased risk of dementia compared to the rest of the population. One study found that approximately 40 percent of people over age 65 who were diagnosed with mild cognitive impairment developed dementia within three years.
High Blood Pressure (Hypertension)
Several studies have shown that high blood pressure medicine reduces the odds of dementia in elderly people with high blood pressure. One large European study found a 55 percent lower risk of dementia in people over 60 who received drug treatment for hypertension. These people had a reduced risk of both Alzheimer's disease and vascular dementia.
Atherosclerosis is the buildup of plaque -- deposits of fatty substances, cholesterol, and other matter -- in the inner lining of an artery. Atherosclerosis is a significant risk factor for vascular dementia, because it interferes with the delivery of blood to the brain and can lead to stroke. Studies have also found a possible link between atherosclerosis and Alzheimer's disease.
High levels of low-density lipoprotein (LDL), the so-called bad form of cholesterol, appear to significantly increase a person's risk of developing vascular dementia. Some research has also linked high cholesterol to an increased risk of Alzheimer's disease.
Diabetes is a risk factor for both Alzheimer's disease and vascular dementia. It is also a known risk factor for atherosclerosis and stroke, both of which contribute to vascular dementia.
Several recent studies have found that smoking significantly increases the risk of mental decline and dementia. People who smoke have a higher risk of atherosclerosis and other types of vascular disease, which may be the underlying causes for the increased dementia risk.
Studies also have found that drinking large amounts of alcohol appears to increase the risk of dementia. However, other studies have suggested that people who drink moderately have a lower risk of dementia than either those who drink heavily or those who completely abstain from drinking.
Homocysteine Levels in the Blood
Research has shown that a higher-than-average blood level of homocysteine -- a type of amino acid -- is a strong risk factor for the development of Alzheimer's disease and vascular dementia.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
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