I'm always assessing how well my patients manage to balance on one leg, in two different ways; with one foot slightly lifted off the floor but also with the knee lifted as high as the belly button.
If someone balances well both sides it tells me a lot. First, they very probably have good spinal function, or at least very well coping spinal function. Second, they have very good reflexes and sensation coming from the lower legs and feet. Finally, their brain (especially the cerebellum) and inner ear mechanisms are coping well.
In fact, you can conceive of the balance mechanism as like a computer, with the cerebellum as the main chip, and the 'inputs' being all these other factors (vision, inner ear, sensation and reflexes from the body). Vision also has a big input into the balance mechanism; though it is perfectly possibly to stand on one leg with your eyes closed we know that people who are developing poor balance because of defects in one of these other areas will wobble if they close their eyes (for example, when they are washing their hair in the shower).
We know that poor balance will have its origin in deficiencies in one or more of these areas, and also that poor balance is an inportant predictor of falling risk in 60+ individuals (for example, where you stumble over a kerb and don't quite manage to right yourself).
So a patient should, at least once every few months, self-assess how good they are at balancing on one leg so that they can keep an eye on what is - after all - a core competence.
But now we hear (from the Daily Telegraph today) that poor balance may be quite a good predictor of dementia and stroke. The link appears to be that as micro-bleed activity starts to develop in the brain (way before the development of symptoms of stroke and dementia which eventually it may lead to) it subtly starts to affect balance competence - because the cpu referred to above doesn't work as well.
So, if you find you can't balance well, start practicing. If the problem lies in one of the 'inputs' referred to above, you will quite quickly start to improve (if you persist!).
But, if you don't improve, it might be worth bearing in mind the above?