I’m having a busy week writing information booklets for the friends and family of people with schizophrenia. I’ve not had a lot of time to write a blog post, so the following information comes with many thanks to Alzheimer’s Australia.
Why do some people develop dementia, while others live to a ripe old age with their mind as sharp as a 20 year old? We don’t yet know the answer to this question. What we do know is that several things affect your risk of developing dementia – your age, your genes, certain health factors and your lifestyle.
Old age is the largest risk factor for dementia
Dementia mostly affects older people, and the risk of dementia increases with increasing age. The older you are, the more likely you are to be affected by dementia. Approximately 1 in 70 people aged 65-69 have dementia. Nearly 1 in 4 people aged 85-89 have dementia.
It is rare for someone under 65 to have dementia, but it does occur at younger ages and we call this ‘younger onset dementia’.
Your genes may affect your dementia risk
People often wonder whether dementia is inherited. The answer for most of us is, no. The common forms of dementia are likely caused by a combination of genetic and environmental factors.
If you have a family history of dementia, you have a higher risk of developing it yourself compared to people with no history of dementia in their family. That doesn’t mean that you will definitely get it, just that you have a slightly increased risk.
Where does this increased risk come from? There are ‘susceptibility genes’ that we might inherit from our parents that increase the risk of developing dementia. Several susceptibility genes have been found, and there are likely to be others.
Some people with susceptibility genes will develop dementia but others won’t. And some people will develop dementia even though they don’t carry these genes. So they are just a risk factor, not a cause of dementia.
There are a few very rare forms of inherited dementia. In these families, a particular gene is passed down that directly causes dementia.
Familial Alzheimer’s disease
One rare form of Alzheimer’s disease is passed from generation to generation. This is called Familial Alzheimer’s disease (FAD). If a parent has a mutated gene that causes FAD, each child has a 50% chance of inheriting it. The presence of the gene means that the person will eventually develop Alzheimer’s disease, usually in their 40s or 50s. This form of Alzheimer’s disease affects an extremely small number of people – probably no more than 100 at any given time among the whole population of Australia.
Three genes have been identified which, if mutated in certain ways, will cause FAD. These are called presenilin 1 (chromosome 14), presenilin 2 (chromosome 1) and the amyloid precursor protein gene (APP) on chromosome 21.
If familial Alzheimer’s disease is suspected
Genetic testing can identify specific changes in a person’s genes. This test can tell if a person has FAD and if a child has inherited the changed gene from a parent and will develop the disease in the future. It cannot determine when the symptoms will begin.
It is essential to ensure that suspected cases in the family have, or have had, Alzheimer’s disease and not some other form of dementia. This can only be done through a medical examination, or a careful analysis of past medical records if the person is no longer alive.
Many thanks to Alzheimer’s Australia for letting me use this content … check them out at www.fightdementia.org.au
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About Dr Sarah
I’m an Oxford University-educated neuroscientist, presenter of ABC Catalyst, director of The Neuroscience Academy, and author of The Women's Brain Book. The neuroscience of health, hormones and happiness.
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correct, old age is the main risk factor. As we age, the memory starts getting weak, which leads to this disease dementia.
My psychiatrist has diagnosed my complaint as Alzheimer’s Disease, much to my deep disappointment. I was born in July 1933 and am therefore six months from my 83rd birthday. I was always in the top classes at school and although I left school at age 15 with only the Intermediate Certificate, I have advanced my education and obtained a bachelor degree from Macquarie University Sydney, in my early forties. I joined the Royal Australian Air Force when I was eighteen years old and served for twelve years. I was chosen and trained as an Aircraft Radar and Wireless Technician. A high IQ is required for this profession at least as high as that required for training as a fighter pilot. But a fighter pilot gets his satisfaction from converting any emotions of fear to that of satisfying thrill. I served twelve years in the Air Force and after that I used my technical knowledge in selling complex electronic equipment. I still have the mental competence to comprehend much technology, but I now have a difficulty coping with space and time. If I do not discipline my thinking I may assume that a previous appointment with my psychiatrist (for example) had occurred long ago in the past wherein, in reality, it had been only a matter of a few weeks. I am generally active. I participate in a Pilates exercise group twice a week and I am on the Committee of my Air Force Squadron Association. I am a practicing artist and have been so for about twenty-five years. I draw the figure (live models, both genders) for one full day each week; I cut my own lawn, weed my gardens and do all my own daily housekeeping. I am computer literate and I enjoy reading good literature. I do tire early in the day, but do not “take a nap.” Not ever! I sleep about six hours each night and sleep with the aid of a prescribed Constant Air Pressure (CPAP) machine. I lost my wife of 45 years to Ovarian Cancer thirteen years ago and have since lived alone. I have a few close friends of both genders and many other friends within my neighborhood.I have one close female friend who lives in another State, but we do talk on the phone quite frequently .I am considering returning to my high school algebra text-books, if I can locate them. Otherwise I will buy new ones. Solving math problems is very satisfying. What else do you think I should do? (Perhaps I should seek out comedy shows on Television or the movies), I am not really a genuinely happy person any more. At my most recent meeting with my psychiatrist he told me that there had been no change to the detriment of my mental state over the previous six moths. I have another appointment at a further six month interval and feel strongly that there will be ‘no change’ once again. From my own observation, I feel that I am forgetful about some things, but not of others. I need to refer to my appointment book frequently to recheck the times of imminent commitments, but with others. I belong to a gymnasium and have an hour of “Pilates ‘ exercises twice each week. I keep a journal, but it is more than just a narrative of happenings, it is also a log of my thoughts. I need to be happier about the coming of the end of my life than I am. I don’t enjoy reading text books about coping with death, such as those which my daughter steers my way. I like to live as though I will live for a thousand years, rather than live as though I may die tomorrow. As the negro pianist, Ray Charles, once said, ” I don’t mind bein’ blind, just so long as I ain’t black”. Have a great day. Rod Moffet.
[…] Deborah asks Sarah as we move north of our 40s what preventive measures can we take to try and avoid dementia. […]
Excellent blog for dementia.
Right, the biggest risk factor is old age. As we get older, our memories begin to deteriorate, leading to dementia.
Great article source to read. Thank you for sharing this.