"The first paper from the Radcliffe Infirmary Accident Department, Oxford8 was a retrospective study of people who sustained injuries as a result of horse riding related accidents, who attended the Accident Department and were admitted to hospital.This was followed up by a comparison 20 years later by Chitnavis et al 9 who undertook a prospective study of attendance at the Accident Department in 1991. They found a reduction in total admissions of 46% because of a fall in head injuries most likely due to the use of riding helmets. "
That's 46% reduction of total hospital admissions. So if you wear a helmet you are less likely to be admitted to a hospital. Since they link this to helmet wearing it seems to follow if you wear a helmet you are less likely to have a serious enough injury to be admitted to a hospital. Me, I would rather go home after a fall !! This in itself seems to be a good reason to wear a helmet.