A MAJOR epidemiological study has revealed a striking geographic overlap between amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), pointing to shared environmental risk factors.
Uncovering Hidden Patterns Through Statistical Insight
Although ALS and MS have long been considered separate diseases, one neurodegenerative and the other autoimmune, the new findings challenge this traditional distinction. Historically, MS has shown a clear north–south gradient, unlike ALS, whose pattern was thought more random. By analysing US mortality data along with demographic and geographic information, researchers have discovered that both disorders follow almost identical spatial distributions. This previously unseen link was masked by a phenomenon called Simpson’s paradox, in which strong gender-specific correlations were obscured when data were pooled. Both men and women individually showed correlation rates exceeding 70% between ALS and MS, but these links were hidden in combined datasets. Such results suggest that long-assumed differences between the diseases may have overshadowed deeper, shared environmental mechanisms that warrant closer investigation.
Environmental Factors Beyond Latitude
To evaluate potential causes, scientists combined national mortality data from the US Centers for Disease Control and Prevention with global information from the World Health Organization. Remarkably, the same correlation patterns emerged worldwide. While earlier research attributed MS distribution to sunlight exposure or vitamin D deficiency, this study found ALS and MS to be more strongly related to each other than to latitude alone. This points to influences that coincide roughly with geographic gradients. Possible culprits include viruses, parasites, molds, and algae, as well as human-related factors such as agricultural chemicals, mining, industrial emissions, or pollution of fisheries.
Shared Clues for ALS and MS
These findings raise important questions about why two clinically distinct conditions appear to share spatial and environmental profiles. If ALS and MS share an external trigger, understanding that link could unlock new preventative or therapeutic strategies. As researchers continue to analyse environmental datasets and refine exposure models, this unexpected connection may illuminate broader principles underlying neurodegeneration and immune-mediated brain injury – bridging two diseases once thought unrelated.
Reference
Schilling MA. The geographic association of multiple sclerosis and amyotrophic lateral sclerosis. Scientific Reports. 2025;DOI:10.1038/s41598-025-18755-8.
