Increasing age is the greatest known risk factor for Alzheimer's. Alzheimer's is not a part of normal aging, but your risk increases greatly after you reach age 65. Nearly half of those older than age 85 have Alzheimer's.

People with rare genetic changes that virtually guarantee they'll develop Alzheimer's often begin experiencing symptoms in their 40s or 50s.

Family history and genetics

Your risk of developing Alzheimer's appears to be somewhat higher if a first-degree relative — your parent or sibling — has the disease. Scientists have identified rare changes (mutations) in three genes that virtually guarantee a person who inherits them will develop Alzheimer's. But these mutations account for less than 5 percent of Alzheimer's disease. Most genetic mechanisms of Alzheimer's among families remain largely unexplained. The strongest risk gene researchers have found so far is apolipoprotein e4 (APOE e4). Other risk genes have been identified but not conclusively confirmed.

Sex

Women may be more likely than are men to develop Alzheimer's disease, in part because they live longer.

Mild cognitive impairment

People with mild cognitive impairment (MCI) have memory problems or other symptoms of cognitive decline that are worse than might be expected for their age, but not severe enough to be diagnosed as dementia. Those with MCI have an increased risk — but not a certainty — of later developing dementia. Taking action to develop a healthy lifestyle and strategies to compensate for memory loss at this stage may help delay or prevent the progression to dementia.

Past head trauma

People who've had a severe head trauma or repeated head trauma appear to have a greater risk of Alzheimer's disease.

Lifestyle and heart health

There's no lifestyle factor that's been conclusively shown to reduce your risk of Alzheimer's disease.

However, some evidence suggests that the same factors that put you at risk of heart disease may also increase the chance that you'll develop Alzheimer's. Examples include:

  • Lack of exercise
  • Smoking
  • High blood pressure
  • High blood cholesterol
  • Poorly controlled diabetes
  • A diet lacking in fruits and vegetables
  • Lack of social engagement

These risk factors are also linked to vascular dementia, a type of dementia caused by damaged blood vessels in the brain. Working with your health care team on a plan to control these factors will help protect your heart — and may also help reduce your risk of Alzheimer's disease and vascular dementia.

Lifelong learning and social engagement
Studies have found an association between lifelong involvement in mentally and socially stimulating activities and reduced risk of Alzheimer's disease.

Factors that may reduce your risk of Alzheimer's include:

  • Higher levels of formal education
  • A stimulating job
  • Mentally challenging leisure activities, such as reading, playing games or playing a musical instrument
  • Frequent social interactions

Scientists can't yet explain this link. One theory is that using your brain develops more cell-to-cell connections, which protects your brain against the impact of Alzheimer-related changes. Another theory is that it may be harder to measure cognitive decline in people who exercise their minds frequently or who have more education. Still another explanation is that people with Alzheimer's disease may be less inclined to seek out stimulating activities years before their disease can be diagnosed.

Jan. 19, 2013