Unfortunately...
http://www.msn.com/en-us/health/healthtrending/this-is-one-of-the-earliest-signs-you’re-getting-old/ar-AAnGRIp?li=BBnba9O
That's why it's crucial to understand one's own body, while one still has the
innate instincts to feel the nuances, to know what good balance really entails.
Oftentimes, it's quite contrary to what one is taught.
Yes but what is considered to be "healthy" people by a lot of studies is just "average with no significant health problems". Plus typically the average person with no significant health problems doesn't engage in regular activities which whould require very much vestibular function. It's like a lot of other things in the body - if you don't use it, it'll slowly deteriorate.
I know plenty of older folks who dance regularly who have only continued improving in their dancing and have a better spatial awareness and body control than when they started. It's a lot of them are social dancers but a lot do also compete in the Senior categories. In terms of top level pro's, there are also people in their 40s, Katusha and Mirko for example. There are also plenty of pro athletes over 40 in different sports that continue being competitive, Bjorndalen in skiing for example.
But what do I know, I'm not even close to 40...