MS Incidence Rate on the Rise?

This week's mailer from the MS International Federation had a report entitled "Increasing frequency of multiple sclerosis in Catania, Sicily: a 30-year survey."  The report stated that (regarding Catania's MS incidence rate), "Overall the authors found that during the last 30 years the incidence of MS in this population increased from 1.3/100,000 during the first 5 years of the study (1975-9) to 7.0/100,000 during the final 5 years (2000-4), suggesting that the incidence of MS is still rising and supporting data from elsewhere."

My question is this: Is the MS incidence rate truly on the rise or are technological advancements simply allowing for more MS diagnoses? 

In 1975, the year this study began, I would argue that less people were diagnosed with MS because technology was not good enough to accurately diagnose a person with MS, except in the most obvious cases.  As we know, MS is generally diagnosed after ruling out all other possible diagnoses.  Maybe in 1975, doctors were just unable to accurately diagnose MS in the way that they can today.  MRI technology has gotten better - allowing us to see more of the brain.  Also, I would argue that MS is better understood today than in 1975, which probably leads to more diagnoses. (clearly, there is still plenty that we are still learning about MS, but certainly we know more now than in prior years).  In addition, some people may have ignored initial symptoms and waited years before going to the doctor and getting a diagnosis.  Maybe people are just more apt to go to the doctor earlier on.  It seems as though there could be a number of possibilities.  

In conclusion, I really don't know how we can be sure that the incidence rate is rising.  Clearly, the number of people diagnosed with MS is rising, but does that truly mean that the incidence rate is on the rise?