For Alzheimer’s disease (AD), age is by far the greatest risk factor. Most individuals with the disease are 65 or older, and the likelihood of developing AD doubles about every 5 years after age 65. After age 85, the risk reaches nearly 50%.
Another important risk factor for AD is family history. Research has shown higher risk among those with the first-degree relatives with AD. The risk increases if more than one family member has AD. There are several known genetic risk factors for AD including apolipoprotein E4 genes (ApoE4). A single E4 gene increases the risk of AD by 3-fold. However, a single E4 gene increases the risk of AD by 10-fold if an individual has also had a head injury with loss of consciousness. By contrast, head injury with loss of consciousness in persons with no E4 genes only increases AD risk by about 2-fold.
Currently, testing for genetic risk of AD is not widely done in individuals without symptoms. However, there are certain circumstances where one may wish to know one's genetic risk for AD, including but not limited to:
In these situations, and possibly others, knowing your genetic risk for AD may be helpful. However, if you are the kind of person who could be strongly emotionally affected by finding out your genetic AD risk, then it may not be recommended to do so.
Although risk factors such as age, gender, and genetic disposition cannot be modified, there are many other modifiable or preventable risk factors for AD and other causes of cognitive impairment or dementia.
It is important to know your risk factors and manage them effectively. Recent studies show that the accumulation of beta amyloid plaques in the brain, a major mechanism thought to cause Alzheimer's disease (AD), could begin as early as 30 years before the first symptoms appear. As such, it is never too early to begin a preventative effort.