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Risk factors for dementia

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Tanner Marshall.

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Video transcript

- [Voiceover] When something increases the chance that you'll develop a certain disease we call it a risk factor, right? Because essentially it increases your risk or puts you at a higher risk for developing that disease. By far, the most common risk factor for Alzheimer's disease, vascular dementia, and other types of dementia is age. Dementia is very rare in people under the age of 65 years old but becomes very common after age 80. Unfortunately for us, the fact that we age over time is a risk factor that's completely out of our control,right? Even more unfortunately, the reason as to why this risk of developing dementia increases as we get older is mostly unknown. And another risk factor that tends to be mostly out of our control is family history. So here's you. Here are your parents. Here are your brother and your sister and here's your child. If any of your family here has developed dementia, let's say Alzheimer's disease because that's the most common, then you're gonna be at a higher risk for developing the disease yourself. So say someone else in your family also has developed Alzheimer's, then the risk of you developing Alzheimer's grows even more and this can be the result of environmental factors like how or in what setting you were raised since it's probably going to be a similar setting for your immediate family, right? And with Alzheimer's in particular, scientists are well aware that specific genes are involved even further Alzheimer's disease has both what we call risk genes and deterministic genes. Now risk genes are defined just like a risk factor. If you have this specific risk gene, then you're going to be more likely to develop a certain disease but you're not necessarily going to develop it, you're just gonna be at higher risk. So the risk gene that scientists have found that have the strongest association with developing Alzheimer's disease is called Apolipoprotein E-E4 and a lot of times you see it shortened to APOE-E4. This APOE gene helps us make molecules called lipoproteins which help carry fats and cholesterols through the bloodstream. Maintaining normal levels of cholesterol is very important for helping to prevent a variety of disorders. Now there are three slightly different versions to this gene also called alleles. You have E2, E3 and E4 and it's the E4 type that increases your risk of Alzheimer's. So if you were to inherit one copy of this allele you'll be at a greater risk for developing Alzheimer's and if you inherit two copies, you'll be at even greater risk. It's been suggested that this gene is a factor in about 20-25% of all Alzheimer's cases. So that's the major risk gene, right? Deterministic genes, on the other hand, directly cause a particular disease. In other words, it determines that the disease will be present and essentially guarantees that anyone that inherits it will develop the disorder. As applied to Alzheimer's disease, this is called familial Alzheimer's or sometimes early onset Alzheimer's as it can often happen before age 65. Now scientists have discovered that this can be caused by a mutation in at least one of three genes. You can have a mutation in amyloid precursor protein or APP, Presenilin-1 or PS-1, or Presenilin-2 or PS-2. When any of these genes are mutated or altered large amounts of amyloid plaques tend to build up and these are a major component of Alzheimer's disease, right? Fortunately though, familial or early onset Alzheimer's resulting from a deterministic gene is very rare. And there is always some evidence to suggest that those with Down Syndrome have an increased risk for developing Alzheimer's disease because Down Syndrome occurs when someone has an extra copy of chromosome 21 in every cell which means that many of the genes in their cells have three copies instead of the usual two and that includes the amyloid precursor protein gene. Although that's still fully understood, it's thought that this extra gene might account for an increased production of amyloid plaques and therefore, increase the risk for Alzheimer's disease. Now some of the risk factors for dementia and Alzheimer's, however, are, in fact, in your control. Many experts are starting to reveal trends includes that, start to hint at, other lifestyle and wellness choices that can have a significant influence on your risk of developing dementia. And one big, big risk is head trauma and there is a very strong link that exists between head injury and dementia later on in life, especially when the trauma is repeated like in high-impact sports like football or soccer or when loss of consciousness is involved. With that said, protect your brain! It's really important! And another risk factor is actually heart trauma. Scientists and health professionals are continuing to see links between brain health and heart health. Many of the risk factors that lead to heart disease also apply to dementia but why is that? Well, most types of heart disease, your heart gets less efficient at pumping blood, right? Well, if less blood's getting to brain, it's gonna have an increased risk of damaging your brain cells and developing some sort of dementia. So things like poor diet and obseity, diabetes, smoking and heavy alcohol use will increase your risk of both heart diseases and dementia. And if there is some sort of heart conditions that already exist like atherosclerosis or high blood pressure, your risk for dementia increases as well. That being said, protect your heart! It's also important.