What is dementia?

Dementia is an umbrella term. And it means that it’s something that’s progressive, so it gets worse over time. And it’s neurodegenerative, which is a medical way of saying your brain cells die. So dementia is any disease where your brain cells die more and more over time. There’s lots of different types of dementia. And on one level, they’re defined by which bit of the brain is being affected. So different bits of our brain do different things. So if the memory bit of your brain is affected by a disease, your memory will get progressively worse but your other skills will stay OK for some time.

If the back of your brain is affected, that’s where we think about vision and where things are in space, then those skills will be affected, but your memory and other skills will stay pretty good. If the front of your brain is affected, your behaviour and your social skills will decline, but your memory might actually be really, really good for some time. So there’s lots of different kinds of dementia. They’ve all got different names. Dementia is just this overarching term that means your brain is declining progressively. By far the most common cause is Alzheimer’s disease. Alzheimer’s disease one specific form of dementia. And it tends to be a problem that starts with memory.

And over time, one tends to get other things involved, so not just memory, but other bits of thinking. And over time, it becomes more the whole brain, so global cognitive impairment. Probably about 50% or 60% of people have Alzheimer’s disease in terms of the whole group of people with dementia. And if you think about the other causes, the next in line, people who develop problems with thinning of their blood vessels, what’s called vascular dementia or vascular cognitive impairment. After that is a condition called Lewy body dementia. So that’s a condition that looks a bit like Parkinson’s disease, but tends to start with dementia rather than starting with changes in movement, slowing of movement that you see in Parkinson’s disease.

And then fourth in line is frontotemporal dementia, so a condition that is less common as you get older. But it is a condition that affects your behaviour and your language and in a younger age group, so under 65, tends to be almost as common as Alzheimer’s disease, so one of the more common types. Those four things together probably account for somewhere around 95% of all causes of dementia. And then that 5% is lots of other things, so probably hundreds of other things which are all relatively rare, but can cause this acquired progressive problem in your thinking and behaviour.