Increasing incidence of multiple sclerosis in the province of Sassari, northern Sardinia

Sardinia is a high-risk area for multiple sclerosis (MS),
with prevalence rates of 150 per 100,000 population. The
study included 689 MS patients (female-male ratio 2.6)
with disease onset between 1965 and 1999 in the province
of Sassari. The mean annual incidence rate increased
signifi cantly from 1.1 per 100,000 population in
1965–1969 to 5.8 in 1995–1999, with no signifi cant difference
for gender and province sub-areas. The mean age
at onset increased signifi cantly during the same period
from 25.7 to 30.6 years, while the proportion of patients
with progressive initial course declined over time. The
marked increase of MS incidence and the change of MS
clinical phenotype over time cannot be explained by ascertainment
bias only, thus pointing to a corresponding
change in the distribution of exogenous risk factors in
this highly genetically stable population.