A new study provides more evidence that exposure to common solvents, like paint thinner and varnish, can increase the risk of multiple sclerosis (MS), particularly for people already at risk from other factors. Karolinska Institutet researchers assessed 2,042 people in Sweden who’d recently been diagnosed with MS and 2,947 who hadn’t. Participants were asked about their previous exposure to solvents and whether they’d ever smoked, another major contributor to MS risk. Participants’ blood was also tested for a gene variant linked to increased MS susceptibility.
The researchers' findings suggest that genetic risk and environmental contributors work together, amplifying risk beyond the sum of the individual factors. As a result, people with all three risk factors—exposure to solvents, the gene variant, and a history of smoking—were 30 times more likely to develop MS than people with none of them. We spoke with study author Anna Hedström to learn more.
ResearchGate: What led you to look into a possible association between MS and exposure to solvents?
Anna Hedström: Smoking is an established risk factor for MS, and one possible mechanism linking smoking and MS susceptibility involves chronic lung irritation. So we wanted to study the influence of another source of lung irritation, organic solvents, on MS risk.
Because we have previously observed that smoking influences MS risk to a much greater extent if you also carry MS risk HLA genes, we also wanted to study whether a gene-environment interaction occurs with organic solvents and these genes.
RG: What did you find?
Hedström: We confirmed the relationship previous studies had found between exposure to organic solvents and increased MS risk. We also found that a gene-environment interaction does take place: The combined effect of the MS risk genes and exposure to organic solvents is much higher than the sum of the individual effects of the exposures. Among those who carry the MS risk genes, there was also a synergistic effect between organic solvents and smoking.
RG: Were you surprised by the results?
Hedström: The interaction between organic solvents and smoking among those with a high genetic risk for MS was not expected. And the 30-fold increased risk among those with all risk factors compared to those who were unexposed was higher than we expected.
RG: Did the extent of exposure matter? For example, would occasional home improvement pose less of a risk than working as a professional painter?
Hedström: Yes, there was a dose-response relationship—the risk of the disease increased with increasing exposure to organic solvents.
RG: Can people with these MS genes do anything to protect themselves if they are frequently exposed to solvents?
Hedström: The strongest genetic risk factor for MS is common; approximately 30 percent of the population carry this gene. However, MS is a rare disease, and most people with this gene do not develop MS. Those with a family history of MS may have a greater genetic susceptibility. What they can do to reduce risk is avoid both smoking and unnecessary exposure to organic solvents—and especially the combination of these exposures.
RG: Do these findings have any applications for potential treatments?
Hedström: More research is needed to understand the mechanisms behind our findings, but increased knowledge about disease-mediating mechanisms will increase the opportunity to develop new treatments in the future.
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