The natural history of multiple sclerosis: a regional study with some longitudinal data.

A regional survey of multiple sclerosis (MS) patients in Wellington, New Zealand in 1983 identified 245 patients, giving a prevalence (all categories included) of 72 per 100,000. Retrospective review of the history and medical records identified a poorer prognosis for disability where there was progressive onset of symptoms, secondary progression after a remitting phase, older age of onset (40 years or more), or a motor syndrome involving the limbs at presentation. In 1983 follow up data were obtained on 96 patients who were seen during a previous survey in 1968. For those with definite or probable MS, progression to severe disability (Kurtzke disability status scale (DSS) 6-9) or death (DSS 10) was seen in 26/34 with moderate disability (DSS 3-5) in 1968 and in only 5/29 with mild disability (DSS 0-2). When the analysis is confined to those with symptoms for at least five years in 1968, severe disability or death from MS occurred in 22/30 with moderate and 4/19 with mild disability (chi 2 = 10.8, p = 0.001). It is concluded that the patient's established disability level after five years of illness is a useful, but not infallible, prognostic indicator. From the follow up of the 1968 patients, the probability of MS-related mortality for a given disease duration was calculated. Using this survival distribution to adjust the disability ratings in the 1983 population, it was found that the proportion with mild disability decreased steadily with increasing disease duration, reaching 14% when the disease duration was more than 25 years.