Family history
tt is important to stress that having a family history of Alzheimer’s does not automatically mean you will get the disease. It does mean though if one or more of your close relatives lived with Alzheimer’s in general there is a genetic risk component and you have a slightly increased risk of developing the disease. Studies have shown the risk increases by approximately 30% if you have a parent or sibling with Alzheimer’s, when compared to someone with no family history.
This doesn’t sound like a small risk I can hear you saying, but let me talk absolute numbers to explain how the increased risk is indeed actually quite small. In the general population our risk of developing Alzheimer’s by the age of 65 is around 2%, which equates to 2 cases for every 100 people. If a family history of the disease raises your risk by 30%, this will increase the number of cases to 2.6 for every 100. So, without a family history 20 people from 1000 will develop Alzheimer’s, and with a family history, 26 people from 1000 will develop the disease. However, ageing increases our risk far more substantially than having a family history of the disease.
While I’ve just explained the small risk that having a family history of Alzheimer’s actually has on our own chance of developing the disease, there are a rare group of families around the world that have a variant of Alzheimer’s known as early familial Alzheimer’s disease (eFAD), which has a much higher risk of being passed down through the generations.
Geneticists have determined that eFAD is hereditary and develops at an unusually early age – typically in someone’s thirties, forties or fifties, and even more rarely, in their late twenties. Someone diagnosed with eFAD will generally have had a parent with the disease, and their children and siblings may have a 50-50 chance of inheriting it.
Studies of some of these known families around the world have helped us to better understand the mechanisms of Alzheimer’s in general, and in particular the most common non-familial cases of late onset Alzheimer’s in the over 65-year old age group, which account for more than 98% of everyone living with the disease today.
I’ve listed a number of papers below that you may want to dip in and out of that discuss studies on the effect of a family history of Alzheimer’s that may be of interest:
- Donix, M. et.al. (2012). Influence of Alzheimer Disease Family History and Genetic Risk on Cognitive Performance in Healthy Middle-Aged and Older People. The American Journal of Geriatric Psychiatry: Official Journal of the American Association for Geriatric Psychiatry, 20(7), 10.1097/JGP.0b013e3182107e6a
- Ritchie, Karen et.al. “Is Late-Onset Alzheimer’s Disease Really a Disease of Midlife?” Alzheimer’s & Dementia?: Translational Research & Clinical Interventions 1.2 (2015): 122–130. PMC. Web. 4 Sept. 2018.
- Marioni, R. E. et.al. (2018). GWAS on family history of Alzheimer’s disease. Translational Psychiatry, 8, 99.
Having a family history of Alzheimer’s is something we can’t obviously change, but as I discussed in the previous section on the risk factor of Advancing Age, the best way we can minimise our risk of developing Alzheimer’s is to follow the following six simple lifestyle choices. It’s never too late, just make that commitment to become a healthier you.
The Alzheimer’s Society has put together an excellent brochure that outlines helpful ways to reduce your dementia risk. Download your free copy now.