Incidence of multiple sclerosis in Iceland, 2002-2007: a population-based study

We conducted a study to determine the incidence of multiple sclerosis (MS) among the whole Icelandic population during a 6-year period (2002-2007).

We included all Icelandic residents diagnosed with MS during the study period. Cases were identified from records of the only neurology department in Iceland, plus the records of all practicing neurologists and all radiology departments. All patients had experienced at least two confirmed MS relapses (i.e. clinically definite MS) or had primary progressive MS as defined by the Poser criteria.

We identified 136 individuals who met the inclusion criteria, including 102 (75%) women. The mean age at diagnosis was 36.3 years (women 35.7 years, men 38.3 years). Average annual incidence was 7.6 per 100,000 population. All but one patient (99%) had an MRI study done at diagnosis and 61% of these (83/135) fulfilled the Barkhof criteria for diagnosis of MS; one had a normal MRI. A visual evoked potential test was done in 68% (93/136) at the time of diagnosis and 44% (41/93) were abnormal. Spinal fluid was obtained from 78% (106/136), and 75% (80/106) had oligoclonal bands.

A total population study is the most reliable method of determining the spectrum of clinical symptoms and the results of investigations in MS patients at diagnosis.