Background: These investigators estimated the MS incidence (number of cases per year) in the Netherlands in relation to vaccine safety.
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.
“The results of this study are interesting and confirm what we know about MS is other countries; the incidence is increasing in woman and the time to diagnosis has decreased.”
“The increasing incidence amongst woman can be seen with a change in the sex ratio. Why this is occurring is not clear. Some of the increasing incidence can be explained by changes in the rate of smoking amongst woman (increased relative males) and cultural changes (addition of UV blockers in cosmetics). However, the sex ratio changes remains largely unexplained.”
“The lag time diagnosis relates to wider access to neurological services and in particular MRI scans. Another driver is the change in the diagnostic criteria that allows the diagnosis of MS to occur much earlier for example after the first attack. The latter has implications in that more MSers are being diagnosed with less active disease, which is why the overall prognosis of MS is changing, i.e. getting better. The latter is referred to be statisticians as the Will Rogers effect; i.e. changing the diagnostic boundary between CIS and RRMS, by moving the boundary to the left, improves the outcome of both groups. Interesting? I find the Will Rogers effect or phenomenon fascinating!”