After reaching the age of about 50, almost all of us worry from time to time that our memories are beginning to fail. You might find yourself unable to remember someone’s name, or where you left the house keys, and that’s just the beginning.
Before you know it, you’re forgetting to turn off the gas, or struggling to recall passwords and PINs that you’ve been using for years.
If that sounds familiar, take heart from the fact that you are not alone. Next to poorer physical health, memory loss and a declining ability to concentrate are our two greatest fears about getting older.
So when exactly does this start? How fast does it progress? And what capacities remain unaffected?
As a neuroscientist who has long specialised in the study of the ageing brain, I’ll answer these questions over the course of this three-part series, calling on the latest scientific findings to present some often rather surprising statistics and facts. As we will see, for example, the decline in our memory begins much earlier than we generally think.
It’s not all bad news, however. As I’ll explain, there are many practical steps we can take to slow the erosion of brain function. But first let’s look at the physical changes that take place in our brains as we age.
Your shrinking brain
Between the ages of 30 and 90, the volume of the brain shrinks by about 15 per cent. Scientists used to think that this was down to a dying off of the ‘grey matter’, as our neurons (brain cells) are collectively known.
They also believed that no new neurons were generated once you reached adulthood.
But the latest research indicates that most brain cells remain reasonably intact until we die, and that thousands of new neurons are produced daily, even in the older brain — although at a rate that falls by as much as 80 per cent during a lifetime.
While our brain cells do not die off in the way scientists once thought, some of them do appear to start reducing in size, and this begins when we are at a remarkably early age.
Take those involved in storing and retrieving our memories. The general impression is that forgetfulness begins in late middle age. Yet research has established a very different starting date for memory decline. And that — prepare yourself — is around your 20th year.
Scores on memory tests decline gradually between then and the age of about 60. But, after that, they fall more rapidly and some types of memory deteriorate much faster than others, governed as they are by the two parts of the brain most affected by ageing.
These are the hippocampus, a structure shaped a little like a sea-horse and located near the temples, and the pre-frontal cortex, which, as its name suggests, is also to the fore of the brain.
Between them they handle various key memory functions including the ability to remember stories, visualise where you put things, such as the television remote control, or retrace the route to a friend’s house in your mind’s eye.