Hi Tim. I am going to copy this to the medical forum for you so you can see if you have any 'official' response from there.
There are always a lot of 'irrelevant' stuff on offical forms and the like but I suspect its just the CAA covering thier bums and having to include questions like that for legal reasons. I hope someone can come up with a better answer though, would be quite intersting to see why as you ask.