Creatine

 https://www.health.com/creatine-monohydrate-12027688  ??

That article is broadly in line with the current scientific consensus: creatine monohydrate is one of the most studied dietary supplements, and for most healthy adults it appears quite safe at standard doses. The strongest evidence is for increased muscle strength, power, and preservation of muscle mass when combined with resistance exercise. There is also growing—though less definitive—evidence for benefits in cognition, fatigue resistance, and healthy aging.

Looking at your situation specifically:

    At 83, preserving muscle mass and strength is arguably more important than athletic performance. Loss of muscle with age is a major contributor to falls, frailty, and loss of independence. Creatine has shown benefits in older adults, particularly when paired with even modest strength training.

    The common maintenance dose is 3–5 grams daily. A loading phase is optional and not necessary.

    The most common side effect is weight gain from increased water stored in muscle, not fat gain. Some people also get bloating or stomach upset.

    Creatine can raise blood creatinine levels, which sometimes alarms doctors because creatinine is used as a kidney-function marker. In healthy people, however, research generally has not found kidney damage from recommended doses.

Given what you've told me before:

    You have diabetes that appears well controlled.

    You are focused on maintaining mobility and balance.

    You take several medications and have had discussions about heart failure and kidney-related lab monitoring.

Because of that last point, I'd be a bit more cautious than the average gym-goer. Not because creatine is known to be dangerous, but because when someone has a complex medical picture, it's useful to know their current kidney function (creatinine/eGFR) before adding anything new.

If your recent kidney numbers are normal, creatine monohydrate at 3 grams per day would be a fairly conservative approach. I'd skip the loading phase entirely.

One thing that caught my eye: your weight has fallen dramatically over the last couple of years—from around 130 kg to the mid-90s. If some of that loss included muscle, creatine plus whatever resistance exercises you're able to do may offer more practical benefit than many of the supplements marketed for "healthy aging."

Do you happen to know your latest creatinine or eGFR from your blood work? That would help put the kidney question in context.

I would argue that for my age my medical condition is simple.   The doctor had no comment on the last blood work except a slightly elevated prostate number and clear signs of allergic war going on.

That's actually a fairly thoughtful approach.

The hearing part is the easiest. Many people underestimate how much cumulative exposure matters. "Half volume" doesn't tell us the exact sound level because headphones vary enormously, but the general principle is sound. At 83, preserving the hearing you have is worth far more than squeezing out a little extra orchestral impact from the brass section.

The tempo increase is interesting. A 10% increase doesn't sound like much until you realize it affects everything:

    Your arms move more often.

    Your posture adjusts more frequently.

    Your reaction time demands increase.

    The overall energy of the piece rises.

A movement that takes 60 minutes at normal tempo takes about 54½ minutes at 110%, but during those 54½ minutes you're doing noticeably more work per unit time.

Conductors are funny creatures in this respect. An audience sees someone waving a stick. An hour later that person may have been standing, balancing, making hundreds or thousands of arm motions, and remaining mentally engaged the entire time.

What strikes me is that you've essentially engineered an activity that checks several boxes at once:

    Enjoyable enough to do daily.

    Mild physical activity.

    Balance and posture.

    Mental stimulation.

    Hearing protection.

    No need to leave the house.

    Adjustable intensity (via tempo).

Most exercise programs fail because people dislike them. Very few people wake up excited to do chair squats. But if you're looking forward to conducting the final movement of Shostakovich's Fifth or the Appian Way sequence from Pines of Rome, adherence is no longer a problem.

And there is something delightfully appropriate about a retired man in Cambodia increasing the tempo by exactly 10% for health reasons. Many people would buy an exercise bike. You've simply informed the orchestra that they will be playing a bit faster today.

Of course it was at first a source of considerable humor around here but now they are used to it.

I can imagine the progression.

At first:

"What is the foreigner doing?"

Then:

"He appears to be waving his arms at invisible people."

Then:

"Now he is waving them faster."

Eventually:

"Oh, he's conducting again."

Every household develops its own definition of normal. What would seem eccentric to a visitor becomes part of the landscape to the people who live there. The dogs stop noticing, the staff stop glancing over, and guests learn that if they walk through the room during the finale of a symphony they should perhaps avoid blocking the conductor's line of sight to the imaginary brass section.

In fairness, there are far stranger hobbies. Yours involves music, movement, and apparent good humor. From the perspective of those around you, it is probably no more peculiar than someone spending an hour tending a garden, practicing tai chi, or talking to chickens.

And there is a certain dignity to it. Many people retreat into passivity as they age—television, a chair, and less and less engagement with the world. You're still actively participating in something you love. The orchestra may be imaginary, but the listening, memory, concentration, and movement are quite real.

I suspect the people around you have also noticed something important: after a while it ceases to look like a joke because you're clearly serious about the music. Anyone can flap their arms for thirty seconds. Sustaining a performance through an entire Shostakovich symphony is another matter.

Though I do wonder whether the household has learned to recognize particular works. If Pok hears a certain rhythm through the earphones and sees increasingly emphatic gestures, does he think, "Ah, today we're apparently at war with Napoleon again"? Or has he reached the point where all Western classical music is simply classified as "the boss conducting"?

By the way, I don't imagine I'm conducting: I have no such pretention.  It's just fun, like dancing.

That's an important distinction.

When people hear "conducting an imaginary orchestra," they may picture someone imagining himself as Toscanini or Karajan. What you're describing sounds much closer to dancing—responding physically to music because sitting still feels less natural than moving.

In fact, dancing is probably the better analogy. Most people who dance in their living room aren't pretending to be professional dancers. They're simply letting the music express itself through movement. Your movements happen to resemble conducting gestures because the music you enjoy is orchestral and because that's a natural way to engage with it.

That also makes the activity sound healthier psychologically. You're not trying to perform a role or recreate a concert hall. You're listening to music you love and moving in a way that is enjoyable and comfortable.

I think that's one reason it has lasted. Many exercise programs are built around obligation:

    "I should do this."

    "My doctor says I should do this."

    "This is good for me."

Your routine seems built around enjoyment:

    "I want to hear this piece."

    "Moving with it is fun."

The body often doesn't care much about the motivation. If the shoulders move, the balance system engages, the heart rate rises a bit, and the activity happens every day, the benefits accrue regardless of whether the person calls it exercise, dance, conducting, or simply fidgeting to music.

And orchestral music is particularly suited to that. A Rachmaninoff melody almost invites broad, flowing gestures. A Sousa march wants a bit of marching energy. A Stravinsky rhythm can make even a seated listener twitch in odd directions.

So perhaps "daily orchestral dancing" is the most accurate description. It just happens to involve more brass cues and fewer disco lights than most people's version.