Exponential decay

Saturday 24 August 2019

“What’s wrong? Is there something you want to talk about?”

Clara had a look on her face that I have come to recognise. We had just returned from an overnight trip to Sussex for my birthday and she looked concerned.

There was silence for a while. She seemed reluctant to speak but eventually came out with it.

“It’s your driving. You were driving too fast and there were two or three times…”

I interrupted with the typical male response.

“There’s nothing worse than a passenger seat driver. I wasn’t driving too fast. Maybe just over the speed limit, but not by much.”

But then I reflected on it for a minute and put my ego to one side.

"Actually, you're right," I continued. "I'm not safe any longer. At least not on long journeys."

We were only talking about a 1 hour 40 minute drive, but in that time I’d had to stop twice because I had been feeling pretty out of it. Tired and dizzy, I even had a brief nap at a service station. At times I had been driving in a bit of a daze, too fast and with slow reactions.

“From now on, I won’t drive for more than an hour,” I concluded. “Next time we go on a similar journey, either you can drive or we can take the train.”

Currently on a 3 year medical review licence (see previous post cleared to drive), I am legally allowed to drive only until the spring, after which I need to apply to renew my licence. I’m confident it will get extended, but I need to stay safe and that means limiting my time behind the wheel. I’m pleased that I got a couple of driving holidays, in the US and Canada, completed in the last two years, because I don’t think I could manage them now.

I expect that in another two years’ time I will again still be driving but perhaps even shorter distances – maybe I’ll be capping myself at 30 minutes by then. It’s a similar story with other activities, for example running. A year ago I was regularly running 5K. Now I still run once or twice a week but 3K seems to be the comfortable limit.

So I can still do many things, just less and less of them each year. In mathematical terms, this is called exponential decay. It’s the same concept as a half-life. For example, I reckon the distance I can drive and the distance I can run both have a half-life of about 2 years. This means that in 2019 I can do roughly half of what I could do in 2017, like running 3K instead of 6K.

Projecting forwards, I can expect to still be running in 2021, but perhaps only for a mile (1.6K) or thereabouts. Possibly I have got this wrong and the half-life is more like 3 years, meaning I can still run a mile in 2022.

At least, that’s my hypothesis. The term exponential decay sounds bad but, if my hypothesis is correct, this is actually a very good thing. I will still be active for quite a few years yet, just limited in how much I can do.

And with the running, because my mileage is so low and ever-diminishing, I probably never need to buy a pair of running shoes again…

How are you?

Thursday 8 August 2019

The lift doors are about to close but I squeeze in just in time. It’s 7:50am and I am on the way to the fourteenth floor to start my day.

A work colleague is standing in the back corner and she smiles at me. In her early thirties, she is someone I know by name, but not particularly well.

“Good morning,” she enthuses. “How are you?” 

It’s a rhetorical question, one for which a standard response is expected rather than an actual exchange of information. But her manner is earnest, as if she has a genuine interest in my well-being today and I hesitate in my answer. A series of options races through my mind. 

Option 1. I can lie and tell her I’m fine.

Option 2. I can tell her that I had five hours sleep last night, awake since 3am tossing and turning until 6. Again. That I am dreading the day ahead and the thought of another bout of orthostatic hypotension like I had yesterday, almost fainting several times and needing to lie down in the first aid room in the early afternoon. That I am afraid of losing my voice in a client meeting, as has started to happen occasionally. That I’m anxious about the heart palpitations that have returned recently. That I simply want to keep my head down all day and avoid any human interaction until I can slip away home quietly.

Option 3. I say something in between and put a positive spin on it. Something along the lines of: 

“Well actually I’m a bit tired; haven’t been sleeping well this week. But I can’t complain. The sun is shining and I have some holiday coming up soon. How are you? Did you go anywhere nice this summer?”

Option 4. I can invoke a little black humour:

“To be honest I’m feeling pretty crap today.” (Smile.) “I have this disease called Parkinson’s which makes me really tired. But it’s the perfect excuse for leaving work social events early. How about you? Do you have a tale of woe today?”

Option 5. I can babble on like an idiot:

“I can give you the real answer to that question if you like. It’s funny how we all say that but don’t really expect an answer. It’s a kind of ritual isn’t it? Like commenting on the weather. Or talking about pets. A way of making human contact….”

I snap out of my reverie. The initially momentary pause is now starting to become awkward. Decision time. Should I tell her the truth? Should I unload my woes?

But in the end, my response is – of course – the predictable one.

“I’m fine. How are you?”