Verified by 
Whenever someone’s relative is diagnosed with dementia, the ‘will I also get it?’ question inevitably arises. The short answer is ‘probably not’, but the full answer is, as always with these things, rather more complex. If you are of a neurotic disposition, I suggest you stop reading at this point.
First, we have the question of genetic predisposition. In other words, if a parent or sibling becomes demented, does that mean that you will inevitably do the same? Happily, the answer is ‘no’. There are some rare instances where the probability is raised – these apply when a parent develops dementia before they are sixty. Early onset dementia of this kind is rare (it accounts for circa 2% of all dementia cases) and the risk that a child will also develop EOD is increased, but it is never guaranteed. In the vast majority of cases of dementia, genetic inheritance does not seem to play a significant role. For example, identical twins have identical genes, but if one twin develops dementia, there is no firm guarantee that the other one will.
But nonetheless, the chances of any of us developing dementia increase as we get older, and from the age of sixty, this chance doubles every five years we live. If you survive into your nineties, then there is roughly a one in four chance that you will have dementia.
These are sobering figures, but we need to put them in perspective. The statement that a person ‘has dementia’ can be misleading. In the final stages of the condition, people are seriously intellectually compromised, and this is generally how we think of dementia. However, in the earliest stages the signs might be apparent to a trained clinician, but even close relatives might not notice anything amiss, discounting symptoms as being the sort of mild absent-mindedness that stereotypical ageing is supposed to bring. Many people will not move beyond this mild stage before they die, and cold comfort as that is, the idea that people with dementia will inevitably end their days in a residential home or psychogeriatric ward are wide of the mark. In short, even if you are in the minority who develop dementia, it is unlikely to reach a profoundly debilitating stage.
Nonetheless, it cannot be denied that there is a lot of dementia about, and unless an effective drug treatment is found, it will continue to be an unwelcome presence. So is there anything you can do to lower your chances of contracting dementia? The answer is that some things can be done, but others are currently beyond our control. It often surprises people to learn that ‘dementia’ is a collective term for more than fifty conditions that have the same general set of symptoms. Some dementias are caused by exposure to particular toxins. Many of these have not been seen in recent times. For example, exposure to certain chemicals used in the manufacture of hats in the 19th century led to a spate of dementia amongst factory workers (this is the origin of the phrase ‘mad as a hatter’). Following more stringent factory laws, these dementias disappeared. Thus, unless you are e.g. planning to do some bizarre historical re-enactment of 19th century working conditions, then you are never going to get that type of dementia. Other dementias are associated with high blood pressure. Therefore, all the things that doctors tell you about keeping your weight down, eating and exercising sensibly, etc, are a good thing. But the causes of other dementias have no known cause. They might be prions (incredibly tiny organisms that make viruses look huge), they might be something in the environment, we just do not know for certain. We know that people with some genotypes carry an elevated risk of contracting particular types of dementia, but generally these apply to EOD or, in the case of older people, they raise the odds, but do not doom a person to developing the condition. Therefore, to some extent, contracting dementia, given our present state of knowledge, seems to be a matter of chance. It appears that leading an active intellectual life can lower the chances of developing symptoms of dementia, but it is not certain whether that means that actually getting the condition is harder to do, or being brainier helps you cover up the symptoms for longer. I favour the latter explanation, but the jury is out on that one and is likely to be for some time.
So, in summary – nobody is predestined to develop dementia because a relative has it; if you do get it, the chances are high that you will die before it becomes very pronounced; and leading a healthy life full of intellectual stimulation can probably help matters. And if that is still too gloomy for you, then cheer up – you are still more likely to die of a heart attack.
