Newly Identified Environmental Factors Linked to Multiple Sclerosis Risk and Progression
A recent study has uncovered significant associations between exposure to certain environmental pollutants and the risk and progression of multiple sclerosis (MS). The research, which followed 907 individuals with MS and 907 matched controls in Sweden for up to 18 years, reveals that exposure to hydroxylated polychlorinated biphenyls (OH-PCBs) is associated with an increased risk of developing MS, while exposure to per- and polyfluorinated substances (PFAS) may decrease the risk of disability worsening in MS patients.
Understanding Multiple Sclerosis
Multiple sclerosis is a chronic autoimmune and inflammatory disease affecting the central nervous system. In MS, the immune system mistakenly attacks the myelin sheath, the protective layer around nerve fibers, causing a range of neurological symptoms. The disease typically manifests in early adulthood, and patients often experience significant disability over time.
* Relapsing-Remitting MS (RRMS): The most common form of MS, characterized by periods of symptom worsening (relapses) followed by partial or complete recovery.
* Primary Progressive MS (PPMS): A less common form of MS, marked by a gradual worsening of disability from the onset, without distinct relapses.
* Secondary Progressive MS (SPMS): A phase that can develop in individuals initially diagnosed with RRMS, where there is a gradual worsening of disability independent of relapses.
Genetic and environmental factors, such as sex, Epstein-Barr virus infection, smoking, obesity, and low vitamin D levels, are known to influence MS risk. However, these factors do not fully explain the development and progression of the disease.
The Role of PFAS and OH-PCBs
PFAS are a group of synthetic chemicals widely used in industrial and consumer products due to their water- and oil-repellent properties. These compounds are extremely persistent in the environment and can accumulate in human bodies through contaminated food, water, and consumer goods.
PCBs, another class of environmental pollutants, were widely used in the past but have been restricted due to their toxicity. Hydroxylated PCBs (OH-PCBs) are metabolites of PCBs that can exhibit different toxic effects.
Key Findings of the Study
* OH-PCBs and MS Risk: The study found that two specific OH-PCBs (4-OH-CB187 and 3-OH-CB153) were associated with an increased risk of developing MS, independent of sex and immigration status. A doubling of serum concentrations of 4-OH-CB187 increased the odds of MS by 8.1%, while 3-OH-CB153 increased the odds by 5.5%.
* PFAS and Disability Worsening: Higher serum concentrations of certain PFAS compounds, including PFOA, PFOS, and PFDA, were associated with a decreased risk of confirmed disability worsening in both sexes. In males, PFHpS and PFNA also showed a similar association.
* Sex-Specific Differences: The study revealed sex-specific differences in PFAS and OH-PCB concentrations between individuals with MS and healthy controls. Males with MS had lower concentrations of short-chain PFAS, while females with MS had higher concentrations of long-chain PFAS.
* Vitamin D and PFAS: The researchers also explored the relationship between PFAS, vitamin D levels, and MS. They found that the inverse association between PFAS and disability worsening was strengthened when considering vitamin D levels, suggesting that the protective effects of PFAS on disease progression are not fully explained by vitamin D.
* Collection Year Impacts: Concentrations of PFAS and OH-PCBs decreased with the year the blood sample was taken, which reflects the restrictions and phasing out of these substances over time.
Potential Mechanisms
* OH-PCBs and Oxidative Stress: Exposure to PCBs can cause oxidative stress in the brain, potentially contributing to the development of MS.
* PFAS and Immunosuppression: PFAS have been shown to modulate the immune system and cause immunosuppression, which may explain the slower disease progression and lower risk of disability worsening observed in MS patients with higher PFAS levels.
* Testosterone and PCBs: Increased serum PCB153 levels have been associated with decreased serum testosterone levels in males. Lower testosterone levels have been linked to disability in males with MS.
Implications and Future Directions
This study provides valuable insights into the role of environmental factors in MS. The identification of OH-PCBs as a risk factor for MS and PFAS as potential inhibitors of disease progression opens new avenues for research and intervention. Further studies are needed to elucidate the mechanisms by which these chemicals affect MS risk and progression.
Limitations
* The reliance on a single-time serum sample.
* The lack of data regarding body fat.
* The lack of data regarding the number of menstruations.
* The exclusive inclusion of participants from Sweden in this study.
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:
Vaivade, A., Erngren, I., Carlsson, H. et al. Associations of PFAS and OH-PCBs with risk of multiple sclerosis onset and disability worsening. Nat Commun 16, 2014 (2025). https://doi.org/10.1038/s41467-025-57172-3
