Incidence of multiple sclerosis in the general population in the Netherlands, 1996-2008.
BACKGROUND
We estimated the multiple sclerosis (MS) incidence in the Netherlands for better active monitoring of potential vaccine safety signals.


METHODS
A retrospective cohort study (1996-2008) was conducted using a population-based general practice research database containing electronic medical records. Additional information was collected to validate incident probable cases.


RESULTS
In the source population (648,656 persons), 146 incident probable MS cases were identified. Overall incidence rate was 6.3/100,000 person years (py; 95% CI, 5.2-7.2). In the subgroup in which MS could be fully validated, the incidence increased from 4/100,000 py (95% CI, 3-5) in 1996-2004 to 9/100,000 py in 2007/8 (95% CI, 6-16). This increase was highest among women, but not statistically significantly different by gender. The median lag time between first recorded symptoms and MS diagnosis decreased from 32 months (<1998) to 2 months (>2005).


CONCLUSIONS
MS is rare in the Netherlands. In recent years, there was a slight increase in the incidence especially among women during the fertile age. This increase coincided with a decrease in lag time between symptoms and diagnosis, both for men and women. This trend should be taken into account in the interpretation of MS cases occurring in a population where new vaccinations will be introduced shortly.
Department of Epidemiology and Surveillance, Center for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
M A
MA
Kramer
N A T
NA
van der Maas
E M
EM
van Soest
J M
JM
Kemmeren
H E
HE
de Melker
M C J M
MC
Sturkenboom
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology*; D009426:Netherlands / Q000453:epidemiology; D012189:Retrospective Studies; D017678:Sex Distribution