While there is a genetic component to Alzheimer's disease, the disease is not generally considered to be hereditary. The latest report from the Alzheimer's Association is called 2012 Alzheimer’s Disease Facts and Figures. This report includes research data from many sources, and most scientists in the field agree that many factors, not just one, contribute to the onset of the disease.
Among those factors, of course, is family history (heredity); however, it is only one of six causes for Alzheimer's disease. The report states:
Individuals who have a parent, brother or sister with
Alzheimer’s are more likely to develop the disease than
those who do not have a first-degree relative with
Alzheimer’s. Those who have more than one
first-degree relative with Alzheimer’s are at even
higher risk of developing the disease. When
diseases run in families, heredity (genetics), shared
environmental/lifestyle factors or both may play a role.
Clearly genetics can play a part in this disease, but other factors also contribute to Alzheimer's. The other five factors include the following:
- Cardiovascular health - brain function is connected to blood flow, which of course is controlled by the heart.
- Apolipoprotein E-e4 (APOE-e4) - this is a gene protein which not everyone has, but having it is not necessarily a predictor of Alzhaimer's disease.
- Mild cognitive impairment - slight memory loss which might (or might not) be a precursor for Alzheimer's.
- Head trauma/Traumatic Brain Injury - any damage to the brain might increase one's chances of developing the disease.
- Social Engagement and Diet - living a socially engaged life and eating nutrient-rich fruits and vegetables might be helpful in avoiding Alzheimer's (though the research on this one is less conclusive).
In short, while family history (genetics) is one indicator of a predisposition to Alzheimer's disease, it is only one of many; even then, having a relative, even a close one, with the disease is not a guarantee that one will develop it.
Clearly there is no reason to panic, and remember that medical advances are occurring all the time. Alzheimer's is getting a lot of attention in the research world, so in the future things may look drastically different in terms of prevention and perhaps even cure.