I know there will come a time when my wife no longer recognises me. But for now, we both feel blessed | Steven Herrick

My wife – and best friend– of the past 38 years can no longer say the word "hippopotamus" or count backwards from 100, or draw a watch face on a piece of paper. Sometimes she leaves the oven on or forgets to turn off the kitchen tap, and yesterday she wandered into the wrong stairwell of our apartment block.

Two years ago, at the age of 60, Cathie was diagnosed with early-onset Alzheimer's and our lives changed irrevocably. There were no soothing words from the family doctor as a bureaucratic error had sent us the PET scan that confirmed our fears. We read the results together and one of us, the weaker one, cried for a week. Then I pulled myself together and focused on what's important.

Since then, we've sold our Blue Mountains house and moved back to Brisbane where we were born. Cathie wanted warm weather and to be close to her parents, and our youngest son. Most of all, she wanted a dog. Enter Biscuit , a 3.5kg toy poodle and the best anti-Alzheimer's medication invented. Cathie has smiled and laughed more since Biscuit entered our lives than ever. It has left me feeling sheepish that I wasn't attentive or entertaining enough these past few decades, such is Biscuit's unrelenting positivity.

We both feel blessed.

Of course, Biscuit sleeps between us. In the morning, it's often a few minutes before Cathie acknowledges me, such is her focus on the dog. I savour every moment.

Cathie exhibited none of the risk factors for Alzheimer's. She had an excellent diet; an active social life; was very fit – only a few years ago we cycled from Marseille to Norway. We regularly spent months cycling in foreign lands. I'm grateful now that we didn't wait until retirement to travel. Cathie still wants to see the world, still wants to explore exotic tastes and meet new people.

Everyone reacted differently when we told them the diagnosis. Most people have been supportive, aware that regular social events are our lifeblood. Cathie lunches with friends, volunteers at the local Salvos, takes bellydance classes on Friday as a student, even though she taught it for 20 years. We have more dinner party invitations than at any time in our lives.

Alzheimer's is not the loss of memory. A relative, on hearing Cathie's diagnosis, suggested she might have it as well because she sometimes forgets things. I sucked in a deep breath before explaining that Alzheimer's attacks more than memory. Yes, Cathie forget things. But it's the unexpected stuff that hurts. Cathie's language skills have changed dramatically. We don't care that she can't say hippopotamus, but she now rarely speaks in sentences, or can find the accurate word, or pronounce a range of simple and not-so-simple words. My worst fear is that she'll stop trying to verbalise.

I'm learning to never ask "either-or" questions. Beach? Or bushwalk? Cathie will look confused for a few seconds, smile gently and say yes. I'm always humbled at how often she says yes. She's up for anything, as long as Biscuit can accompany us.

Cathie prefers colourful dresses and tops, where previously she favoured what she called the "Greek grandmother look'" of black on black. While I cook most evenings, she's determined to keep trying. We joke whether the result will be of her usual delicious standard or a "Mrs Cropley".

I hate visiting the neurology department of our hospital. They are sensitive and kind and professional, and I watch them measuring Cathie's changes. We use the word "changes". It sounds better than "losses". Last visit they offered Cathie a higher dose of an antidepressant, because despite the headlines of "major Alzheimer's breakthrough", there's little the doctors can do than this, and to monitor the losses. Sorry, the changes.

I've made my living as a writer for 40 years. Since Cathie's diagnosis, I haven't been able to face a new manuscript. Writing a book is more than sitting at a desk each morning. It's living with the characters while walking the dog, or cycling, or doing the shopping. The emotional energy of creating ... I'd rather spend it with Cathie and Biscuit.

Every day I detest Alzheimer's and what's it's doing to the person I love. And every day I'm in awe of how Cathie responds to its ravages. Quietly, stoically, with patience, and sometimes tears, before hugging Biscuit and me.

She kisses my bald head when we sit on the lounge. She never did that before the diagnosis. I know what the disease is taking, but Cathie responds with gestures such as this. When we visit our youngest son and daughter-in-law, she washes the dishes piled on the bench, or helps Joe cook, or chats to Rose about clothes and travel.

I know there will come a time when Cathie no longer recognises me, or Joe, or Rose. Or our eldest son Jack and his wife Emma. Or, shudder, our precious grandson, Billy. She'll sit in a chair staring out the window, at a world shrunken and frail, Biscuit asleep on her lap.

For now, I smile whenever possible. We live one moment at a time, and marvel at the accuracy of cliches.

I prefer today rather than tomorrow.