Our memory is one of our most precious and valued faculties. I’m always full of admiration for people who remember dates, phone numbers, addresses, how to get to places, and above all people’s names, without having to write everything down.

When I was younger I think I had quite a good memory. I could memorize poems and all kinds of useful quotes, I managed to pass various exams, and could find my way around London and other cities quite easily.

Now that I’m over seventy that faculty is definitely deteriorating. I won’t say that my memory loss is more acute than anyone else’s, but when I found myself in town without my handbag (purse in American parlance) on one recent occasion, and having left my smart-phone at home on another, I began to worry.

The affliction of dementia or Alzheimer’s seems to be affecting an ever-growing number of people, some of them comparatively young. I see the suffering of their families and cannot fail to be struck by the devotion and love they display. But the thought that I might end up like that terrifies me, even though I know that losing one’s short-term memory isn’t the only indication, and that some kind of personality change is sometimes also part of the disease.

Apart from trying to keep one’s brain active by always trying to learn something new, the adage ‘a place for everything and everything in its place’ is pivotal in ensuring that one doesn’t waste hours looking for keys or reading-glasses. But what are you supposed to do if you’ve forgotten what that place is?

As chance, or luck, or possibly even fate, would have it, someone posted on Facebook the link to a series of tests for memory loss. Known as SAGE, or Self Administered Gerocognitive Examination, they are provided by the Ohio State University (http://sagetest.osu.edu) and can very easily be printed out so that the individual can test herself in the comfort of her own home.

So I printed the pages out and eventually even summoned up the courage to tackle the tests. To my surprise, I found that they involved recognizing and naming quite familiar objects, giving the names of twelve items in a category such as fruits or vegetables, and doing some simple mental arithmetic akin to calculating the correct change from five dollars if one spends a given sum.

Well, all that’s easy enough, I thought. Ergo, I don’t have Alzheimer’s. Or do I? To my shame, yesterday I forgot to indicate whether the dishwasher was clean or dirty just one day after accusing my husband of committing the same crime. Trying to tell some friends an amusing anecdote I forgot the name of the person about whom I was talking, couldn’t remember the title of a book I wanted to recommend, misremembered the title of a book I myself had written, etc., etc. That’s really scary.

Is it just my imagination, or is there more and more of it around? Is it something in the water we drink or the polluted air we breathe? It is all around us, and it seems to be spreading to an ever-growing number of people, just like one of the plagues in ancient Egypt.

At what point does acceptable weakening of one’s memory become Alzheimer’s? How will I know when I’ve got it? Those SAGE tests are not very difficult. Am I to take it that it’s only when I won’t be able to identify a drawing of a volcano, name twelve animals, and work out how much change I’ll get from five dollars that I should start worrying?

Or will it be too late by then?