What are the risk factors for Alzheimer's disease?

Apparent risk factors for Alzheimer's disease include age, genetic inheritance and gender.

Those older than age 65 are much more likely to get Alzheimer's disease. Genetics also seem to play a role, especially if an immediate blood relative had Alzheimer's, and women tend to get Alzheimer's more frequently because they live longer than men.

Risk factors for Alzheimer's disease include:

• Age. Risk usually rises after age 65 and doubles every five years thereafter.
• Genetics. Heredity is a major factor in only a small number of families, usually those in which the disease begins before age 60. Mutations in three genes are known to cause this type of Alzheimer's: amyloid precursor protein gene, presenilin 1, and presenilin 2. All three genetic mutations increase the production of beta-amyloid, which is deposited in the plaques found in Alzheimer's disease.
• APOE4, one allele (version) of the gene for apolipoprotein E, a protein that plays a role in several biologic processes, has been found in about 40% of patients with late-onset Alzheimer's disease. An estimated 25% to 30% of the population carries APOE4.
• Cardiovascular risk factors. Many studies show physiological conditions that harm the heart and blood vessels also increase the risk of Alzheimer's disease. These include high blood pressure, high cholesterol, obesity, and smoking. All of these factors also increase the risk of stroke, a direct cause of dementia.
• Diabetes. People with diabetes have a greater risk of Alzheimer's disease. Research indicates that this increase in risk may reflect a shared mechanism: a deficiency or dysfunction of insulin, the hormone that enables cells in the body to use glucose.
• Head injury. The microscopic changes in the brains of boxers with dementia resemble those in Alzheimer's disease. The observation has led researchers to wonder if brain injury might be a factor in the disease.

Many studies show that physiological conditions that harm the heart and blood vessels increase the risk of Alzheimer's disease and vascular dementia. These include high blood pressure, high cholesterol, obesity, and smoking, which all increase the risk of stroke, a direct cause of dementia. But such risk factors may also indirectly lead to Alzheimer's disease by other means. Many of these risk factors are also common in people with diabetes -- yet another condition linked to Alzheimer's disease. Most of these factors can be controlled by lifestyle changes, either alone or with medications.