Alzheimer’s disease is a form of dementia that impacts the brain and results in memory loss. In recent years we have been able to study it and its risk factors to calculate the chances of you being affected by the disease. Today we are going to look at how that risk is calculated.
Most people who develop Alzheimer’s are elderly and near the end of their lives. However, this is not always the case. Looking into calculating your risk can be interesting and done using APOE environmental factors and other risks.
It is important to remember that this number is not absolute and can be subject to change. If you are concerned, make sure to consult your doctor.
Inferring APOE status
The Apolipoprotein E (APOE) gene works to protect against Alzheimer’s. The gene has different alleles, some work to protect you from Alzheimer’s, whereas others increase your risk. We all have two copies of this allele, and it's this combination that can determine your risk.
You can find this information out by having genome testing done or speaking to a healthcare professional. If there is a history of Alzheimer’s in your family, it may be offered to you.
Even without genotyping, you can work this out yourself by using genetic programs such as Beagle, which can help give you an odds ratio of developing Alzheimer’s at some point in your life.
Other genetic factors
APOE is a significant genetic risk factor for Alzheimer’s, but it is not alone. The below table shows five other variants.
|
Gene |
Variant |
Risk Allele |
0 |
1 |
2 |
|
CR1 |
rs3818361 |
A |
0.89 |
1.10 |
1.35 |
|
CLU |
rs11136000 |
C |
0.83 |
0.97 |
1.12 |
|
PICALM |
rs541458 |
T |
0.75 |
0.92 |
1.13 |
|
ACE |
rs1800764 |
T |
0.83 |
0.98 |
1.16 |
|
CST3 |
rs1064039 |
C |
0.75 |
0.90 |
1.08 |
The odds are calculated by counting the risk alleles for each variant and times them for all variants.
You can combine this with APOE odds ratios, which will provide a more accurate odds ratio of developing Alzheimer’s.
Environmental factors
Environmental factors won’t influence Alzehimer’s as strongly as APOE, but they are still factors to be aware of.
Most of these risks apply to older people and include vascular disease and head trauma, for example.
Other risk factors apply more widely, such as physical activity, education, and alcohol consumption. The below table looks at these risks.
|
Risk Factor |
Class |
OR |
|
Education |
0-8yrs |
1.36 |
|
9-12ys |
0.98 |
|
|
>12yrs |
0.72 |
|
|
Regular Exercise |
Yes |
0.89 |
|
No |
1.28 |
|
|
Alcohol consumption |
Yes |
0.73 |
|
No |
1.27 |
Some research into genetics and the environment has been done, but not enough to present to you today.
We can consider genetics and the environment separately to multiply ratio odds to get an overall odd ratio.
Prediction and prevention
Using 23andMe’s v2 chip, we can assess the APOE risk through genotype imputation. From this, we can infer a predictive medical factor by using ‘non-medical’ variants. There is the issue of privacy with this and any attempt to separate the medical and non-medical information.
So what do we do with the information? While there is no concrete preventative measures and limited treatment options, it’s down to lifestyle.
Regular exercise and eating less fat and red meat can work to help reduce your risk. As everyone’s risks are different, it’s not necessarily the holy-grail answer for everyone.
It is worth checking with a healthcare professional if you are unsure of what you can do.