Toward Primary Prevention in Multiple Sclerosis: Lessons From a Prospective Study of High-Risk First-Degree Relatives
Multiple sclerosis (MS) is increasingly conceptualized as a disease with a long presymptomatic interval, during which central nervous system (CNS) injury may accumulate before classic clinical diagnostic thresholds are met. Building on evidence that earlier disease-modifying therapy improves long-term disability trajectories, and on randomized trials showing benefit even at the radiologically isolated syndrome (RIS) stage, the next logical frontier is primary prevention—intervening even before MRI-demonstrable CNS lesions or overt neurological symptoms occur. In this context, Laitinen and colleagues leverage the Genes and Environment in Multiple Sclerosis (GEMS) project to address a core translational bottleneck: identifying a sufficiently high-risk population and determining whether that population is both measurable and willing to enroll in prevention studies.
Cohort and Design: The GEMS Platform as a Prevention-Trial “Feasibility Engine”
GEMS is a nationwide prospective cohort of first-degree relatives of individuals with MS, initiated in 2011 with broad inclusion criteria (age 18–50 at enrollment; at least one affected first-degree relative) and no formal exclusions. The present analysis aggregates information from seven surveys collected across approximately 11 years, focusing on 1903 participants with baseline data and variable follow-up. Importantly, this is a geographically distributed, largely questionnaire-driven design, with biological sampling available in a subset. The central analytic strategy is pragmatic: quantify observed conversion to clinically diagnosed MS over time, evaluate risk stratification via genetic/environmental scoring, and interrogate participants’ willingness to join prevention trials—three prerequisites for designing realistic, adequately powered primary prevention studies.
Clinical Outcomes: Conversion to MS and the Incidence Signal in High-Risk Families
Among 1903 first-degree relatives, 141 already carried an MS diagnosis at enrollment, 18 developed incident MS during follow-up, and 1744 remained without a reported MS diagnosis over 8526 person-years of observation. The resulting incidence estimate—211 cases per 100,000 first-degree relatives per year (95% CI 113–308)—is strikingly elevated, reported as ~100-fold higher than sporadic MS incidence referenced by the authors. The MS converter subgroup is clinically informative despite modest size: median time to conversion was 2 years, with a median age of 37 at diagnosis; most were female (89.5%), and diagnostic confirmation was obtained for a substantial subset, with additional rule-based criteria applied when documentation was unavailable. These data provide an empirical anchor for prevention-trial calculations, while also illustrating the key statistical constraint: relatively few converters, limiting granular modeling (e.g., age-adjusted incidence) in the present dataset.
Risk Stratification: The Genetic and Environmental Risk Score as a Recruitment Lever
A central contribution of this work is the use of an integrated Genetic and Environmental Risk Score (GERS) to partition first-degree relatives into subgroups with differential MS risk. The authors report that GERS is higher among participants with MS at enrollment than among those without MS, consistent with the intended construct validity of the score. In the broader GEMS framework summarized here, risk enrichment appears nontrivial: prior work within the project indicated that the top strata of GERS distribution carry roughly double the average familial risk, and in this update the authors explicitly connect such stratification to prevention feasibility, estimating that in an enriched, high-risk subset the annual clinical incidence could approximate 1 in 250—an incidence level that begins to make prevention trials logistically credible. The study also acknowledges an important methodological reality: genotyping in many participants was limited to targeted SNPs, though the authors note high correlation between earlier and expanded genetic risk scoring approaches in a genome-wide subset.
Trial Acceptability: Willingness to Participate Depends on Perceived and Quantified Risk
Beyond epidemiology, prevention trials live or die on recruitment. The authors’ survey findings directly address this: 48% of asymptomatic participants reported willingness to participate in an MS prevention trial, and willingness increased to 75% when participants were presented with a scenario in which genetic testing suggested a substantially elevated (20%) risk of developing MS. When trial modality was specified, acceptability favored established interventions: among those interested in medication trials, willingness was highest for an existing/approved vaccine (89%) and an existing/approved daily oral pill (67%). Under the hypothetical higher-risk scenario, willingness rose further (e.g., 93% for a known vaccine; 75% for a known oral pill), while remaining majority-positive even for novel agents (64% for novel vaccines; 58% for novel oral pills). These gradients are not merely sociological; they are design-critical inputs that inform endpoint selection, risk communication strategy, and the ethical framing of exposure to investigational therapies in asymptomatic individuals.
Biomarkers and Endpoints: Moving Beyond “Clinical MS” Toward Earlier and Mechanistic Readouts
The paper is explicit that genetic and environmental risk alone is unlikely to be sufficient for clinical decision-making, and it emphasizes the need to map early molecular and cellular events that precede clinical conversion. Candidate biomarkers highlighted include immune readouts (e.g., altered T-cell reactivity), compartmentalized inflammatory signatures (e.g., plasma cells/CSF oligoclonal bands), serum neurofilament light chain as a marker of axonal injury, and advanced MRI features such as the central vein sign and paramagnetic rim lesions. Importantly, the study itself lacked MRI acquisition—an acknowledged limitation that also implies possible contamination by unrecognized RIS at baseline. Nevertheless, the authors’ framework is coherent: prevention trials will likely require composite strategies combining (i) risk enrichment (e.g., GERS), (ii) earlier biological endpoints (imaging and fluid biomarkers), and (iii) mechanistically informed intervention classes (including, potentially, vaccination strategies motivated by Epstein–Barr virus epidemiology).
Implications for Next-Generation Prevention Trials: Who to Recruit, What to Measure, and When to Intervene
Taken together, the study’s principal message is operational: primary prevention trials in MS are feasible but must be designed with deliberate enrichment and modern endpoints. The authors recommend oversampling individuals with high GERS, increasing cohort size, incorporating biomarkers (notably MRI) in addition to clinical diagnosis, and shifting recruitment toward younger participants—including adolescents and young adults—because many key risk factors and earliest pathogenic events plausibly occur before age 18. They also contextualize these recommendations within evolving diagnostic frameworks, noting that recognition of asymptomatic MS/RIS in more recent criteria makes prevention-oriented strategies even more relevant. The overarching conceptual stance is probabilistic causation: MS risk factors are not deterministic; therefore, prevention should aim to reduce the probability of initiating CNS-damaging inflammatory cascades rather than targeting a single necessary cause. In that sense, GEMS functions as a prototype infrastructure—quantifying incidence, operationalizing risk stratification, and measuring willingness to participate—that can inform the first generation of truly primary prevention studies in MS.
Disclaimer: This blog post is based on the provided research article and is intended for informational purposes only. It is not intended to provide medical advice. Please consult with a healthcare professional for any health concerns.
References:
Laitinen, A. W., Tozlu, C., Roostaei, T., Diallo, F., Onomichi, K., Son, J., ... & De Jager, P. L. (2026). A Prospective Study of Individuals at Risk of Multiple Sclerosis Informs the Design of Primary Prevention Studies. Annals of Clinical and Translational Neurology.
