At the end of 2020, the results of the research project ‘Project Y’ were published. This project collected data from MS patients born in 1966. Initially, researchers expected to find around 250 people with MS born that year, but they identified 446 cases. This discrepancy led to the hypothesis that the overall number of MS cases in the Netherlands might be higher than previously assumed. With funding from the Dutch MS Society, the prevalence figures were re-evaluated. The analysis revealed that the average MS prevalence in the Netherlands is 210 cases per 100,000 people (or 2.1 per 1,000), double the previously accepted estimate. Amsterdam Neuroscience researcher and PhD candidate Cynthia Lemmens noted, “This increase in prevalence is not unique to the Netherlands; similar trends have been observed in other Northern European countries.”
Improved Registration
The analysis found no evidence of a rise in the incidence of new MS diagnoses in recent years. Instead, the researchers attributed the higher prevalence estimates to other factors. One significant factor is the difference between the number of MS patients registered with general practitioners and those recorded in hospital systems. Patients with milder or more advanced stages of MS are often not treated by neurologists in hospitals. Consequently, reliance on hospital data alone can result in underestimating the true number of MS patients. Additionally, enhanced registration practices and earlier diagnoses - partly due to changes in diagnostic criteria and the availability of more effective treatments - have contributed to the revised estimates.
Critical Insights
The finding that more people in the Netherlands are affected by MS has important implications. For instance, it highlights the need for more healthcare professionals with specialized MS expertise. The research was partially conducted at the request of the MS Patient Association, which can now better understand the size of its constituency. MS neurologist Brigit de Jong emphasized: “This information is also crucial for scientific research. Many MS patients are not included in hospital registries but are recorded by general practitioners. Therefore, if researchers conduct studies on MS and only recruit participants from hospitals, they risk overlooking a significant portion of the population.”
Read the publication in Multiple Sclerosis and Related Disorders: Prevalence and incidence of multiple sclerosis in the Netherlands