I am sorry to hear that both of your grandparents suffer from dementia
. As you know, dementia is a chronic progressive condition in which cognitive function, memory, and social skills are gradually impaired, and the affected person becomes gradually less and less independent.
Most causes of dementia are due to Alzheimer's disease. Development of Alzheimer's disease is a complex process and, in most cases, is only partially influenced by genetics, along with numerous other factors, including environmental exposures and co-existing chronic medical conditions. There are some cases of 'early' Alzheimer's disease, which are strongly inherited, but this is not the typical pattern of Alzheimer's disease developing in elderly people over the age of 65.
In summary, you are probably at slightly higher risk of developing Alzheimer's disease because of your grandparents, but that that risk is not extreme. You should, however, mention this family history to your primary care doctor
at your next physical examination, or even schedule a separate office visit just to talk about this issue. They will be able to make sure you are in generally good health, as staying healthy and controlling medical problems is probably the most important thing you can do to prevent Alzheimer's.