What worries you about getting older?

One by one the more vigorous sports and exacting games fall away. Exceptional exertions are purchased only by a more pronounced and more prolonged fatigue. Muscles may relax, and feet and hands slow down; the nerve of youth and manhood may become less trusty. But painting is a friend who makes no undue demands, excites to no exhausting pursuits, keeps faithful pace even with feeble steps, and holds her canvas as a screen between us and the envious eyes of Time or the surly advance of Decrepitude. Happy are the painters, for they shall not be lonely.

It’s often the same with any new, revolutionary thing. People get stuck as they get older. Our minds are sort of electrochemical computers. Your thoughts construct patterns like scaffolding in your mind. You are really etching chemical patterns. In most cases, people get stuck in those patterns, just like grooves in a record, and they never get out of them.

I don't want to be called a senior citizen, I feel like a spring colt. I don't want to be called a has-been, because there's things I want to do in life. But, I've been there and I'd say, "Don't let the bastards get you down." And they don't anymore, I don't talk to them anymore, so they don't get me down. I've got my family, and I've got so many blessings that I don't think I've earned, that I'm a very happy man.

Certainly not. As a young child, I remember just dreaming about the Nobel Prize, but that was just a dream. It’s not something I would have ever thought was possible for me.

When my father was in his terminal year, I discussed death with him. I recall very clearly his relief that the cancer that was taking him was at least allowing him "all his marbles". Dementia in its varied forms is not like cancer. Dad saw the cancer in his pancreas as an invader. But Alzheimer's is me, unwinding, losing trust in myself, a butt of my own jokes and on bad days capable of playing hunt the slipper by myself and losing. You can't battle it, you can't be a plucky "survivor". It steals you from yourself. And I'm 60; that's supposed to be the new 40.

I saw them recently on their morning walk, and they caused me a pang. I have always wanted a pug and now I can't have one, because buying a puppy when you are too old to take it for walks is unfair. There are dog-walkers, of course; but the best part of owning a dog is walking with it, enjoying its delight when it detects the signs that a walk is imminent, and its glee when its lead is unsnapped and it can bound off over the grass, casting cheerful looks back at you from time to time to make sure that you are still in touch.

I cry a lot because I miss people. I cry a lot because they die and I can't stop them. They leave me and I love them more. ... And so it's what I dread more than anything is the isolation.

I was looking at ageing in action, in black-and-white MRI pixels, death and dissolution foretold, and already partly achieved. My 70-year-old brain was shrunken and withered, a worn and sad version of what it once must have been. There were also ominous white spots in the white matter, signs of ischaemic damage, small-vessel disease, known in the trade as white matter hyperintensities – there are various names for them. They looked like some evil pox. Not to put too fine a point on it, my brain is starting to rot. I am starting to rot. It is the writing on the wall, a deadline.

Being alone and other people getting busier with families and life.

The fact that I smoke.

Mostly the pain. I don’t want to be trapped in a body that hurts.

Pain and loneliness.

Having regrets.

Not feeling old but everyone treating you that way.

The inability to do things for myself.

Forgetting the wonderful memories I have got from throughout my life. Three years ago, I was diagnosed with dementia.

Forgetting things.

Possible dementia.

Losing my mind.

Am I enjoying it too much to find out?