Q: My grandfather and father both suffered from dementia. I’m terrified that it’s coming down the line for me, too. Should I be? And if so, what can I do about it?
Simon Wheeler answers: There are nearly a million people in the UK living with dementia. It’s the UK’s biggest killer. But is it hereditary? That’s a really difficult question to answer simply.
There are diseases out there, such as Huntington’s, that are only ever caused by a genetic mutation that parents can pass on to their children. That kind of dementia is very uncommon. It accounts for less than one in 100 cases. So the simplest answer is no – most dementia is not strictly hereditary.
But then, how do you account for the fact that some families have more dementia than others? Well, there are risk genes for Alzheimer’s disease and other types of dementia. And while gene mutations causing dementia are rare, genes that increase the risk of dementia are relatively common. The difference is that gene mutations are enough by themselves to cause dementia, whereas risk genes just make it more likely to happen.
APOE4 is one of these risk genes. It’s a normal, healthy gene in many ways, but people who have it are more likely to develop dementia than those who have other versions, such as APOE2 or APOE3. If you inherit APOE4 from both parents, you’re a lot more likely to develop Alzheimer’s disease as you get older than someone who doesn’t. Around one in 50 people have this level of genetic risk, and about half of them will have dementia by their mid-80s.
It’s much more common to just have one copy of APOE4 – around one in four people – but this carries a lot less risk, more on a par with other common risk factors for dementia. So it’s not as bad as you might think.
There’s a sensationalist way of presenting dementia – not only that rates are skyrocketing and there’s an epidemic or ‘tsunami’, but also that it’s something you can control by doing the right things. If you pull the right levers, you can go from being one of the people who will get dementia to being one of the people who won’t. Unfortunately, the reality is a little bit different.
How much risk can be mitigated?
Think of dementia risk as a bucket. When you fill that bucket all the way to the top, that’s when you have dementia. Everybody’s bucket will fill to some extent, as they get older. If you have those risk genes, then you’ll start with some of that bucket already partially filled. That means you don’t have as much scope to be unhealthy as someone who doesn’t, and it might be a good idea to make sure that it doesn’t get any fuller by being careful about some of those modifiable risk factors.
There’s a very influential report called The Lancet Commission: Dementia Prevention, Intervention, And Care, which was published last year and tried to estimate the amount of dementia risk that’s caused by modifiable risk factors – that is, things we can change. They estimated that up to around 45% of dementia risk could theoretically be reduced.
Eating well
Diet is an important risk factor, and I would definitely encourage people to have healthy, balanced diets, to keep to a healthy weight and to reduce the risk of diabetes, high blood pressure and high cholesterol. It’s a bit of a cliché, but what’s good for the heart is good for the brain. Everything you might already do to keep your heart healthy – from not eating too much salt to eating lots of fruit and veg – will help to keep your dementia risk down, too.
But the public perception of the influence of diet is overblown. A lot of people think that it’s the key to everything – ‘If only I just ate better and stuck to a Mediterranean diet, I could eliminate my risk.’ Actually, the evidence suggests that the effect of diet is fairly modest in relation to others. For example…
Alcohol
Excessive alcohol consumption is strongly associated with a greater risk of dementia. That’s more than 15 units a week for men and women. And there’s a lot of people in the UK who drink more than 15 units a week, particularly older people. So moderation is key.
Look after your head
Try not to get head injuries. Every traumatic brain injury results in something almost like a bruise on the brain. Neurodegenerative diseases can form around those bruises and increase someone’s risk. That doesn’t mean to say that if you’ve fallen off your bike or a horse then that’s it. But it does mean that wearing a really decent helmet in either of those scenarios is really important.
… and your ears
We know that people with age-related hearing loss become more and more socially isolated. And we know that social isolation is a risk factor for dementia. So there’s a simple chain of causation there. There’s also the possibility that changes in the auditory processing centres of the brain have knock-on effects on the health of the rest of the brain.
So if you can prevent that initial damage to the hearing equipment in the brain, then that might prevent onward damage to the rest of the brain, which would cause dementia. It’s complicated and we’re still not sure how it works, but the overall message is: take care of your ears. Be sensible about noise exposure and wear ear protection when you need to.
… and your eyes
Say you start to develop hearing problems and at the same time your sight deteriorates. Over time, you become more disconnected from the world and more isolated from other people. There’s a plausible mechanism by which that isolation leads to less use of our social and other cognitive skills over time. So look after your vision.
… and your social life
Many people don’t realise how much brain processing power is required to socially interact successfully. There are so many cognitive skills involved in just having a normal conversation.
We hear about the importance of physical activity all the time. But when it comes to dementia risk, it’s really important to stay socially and mentally active. The brain isn’t a muscle, but like a muscle, it needs to be exercised to stay healthy.
… and your mental health
Try and stay mentally well, not just mentally active. There’s evidence that having chronic mental ill health over the life course is not good for your brain.
… but don’t worry about sudoku
There’s this idea that puzzles are the answer – do soduku and all will be well! And fine, if you enjoy puzzles, then do them. But don’t do them as some sort of bitter medicine you need to take to protect yourself from dementia.
What we really want from any form of brain training is for it to have wider benefits – not just making you better at doing puzzles. They should help you to keep doing all the practical normal things in your life – such as making a cup of tea or driving the car – and do them better and more easily.
Unless you really care about puzzles and crosswords, then – unlike socialising – being good at these has limited broader value.
… and don’t bother with supplements
Unless you have a medical condition that means you can’t absorb nutrients naturally, there’s no nutritional supplement that has been shown to reduce your risk of dementia or slow down its progression of dementia.
