As Osteopath to Sidmouth and other festivals I have treated numerous persons, at festivals, with occupations such as Surgeon, Doctor of medicine, Lawyers, Town and County Councillors, Directors of Industry etc.
These all look just like any other "Folkies" and have suffered from the same ailments due to excessive dancing, falls, lifting heavy equipment etc.
You will find that folkies cover the widest possible spectrum of age, income and social standing.
Could I suggest that you contact the Festival Organisers Association as many, particularly large, festivals collate such information to help with Grant applications.
Good luck in your research
Colyn.