Air Pollution Worsens Outcomes in MS and NMOSD, Study Finds

Chutithep Teekaput, MD

(Credit: LinkedIn)

Exposure to fine particulate matter (PM2.5) has been linked to worsening outcomes in patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD), according to a recently published study that analyzed data from 2013 to 2022 in Northern Thailand. Published in Multiple Sclerosis and Related Disorders, researchers observed heightened disease severity, increased need for second-line therapies, and prolonged hospitalizations following air pollution exposure.¹

The study, which included 126 MS and NMOSD exacerbations analyzed for PM2.5 exposure and 135 for PM10 exposure, revealed that PM2.5 significantly worsened clinical outcomes. Patients in the PM2.5 exposure group had higher rates of unfavorable Expanded Disability Status Scale (EDSS) scores at exacerbation (56.3% vs. 23.6%; P <.001) and at 90 days (47.9% vs. 16.4%; P <.001), along with increased gadolinium enhancement (56.3% vs. 36.4%; P = 0.03) and greater reliance on plasma exchange therapy (21.1% vs. 7.3%; P = 0.03).

"The findings suggest that PM2.5 exposure exacerbates MS and NMOSD by increasing disease severity, radiological activity (e.g., gadolinium enhancement), and the need for more intensive interventions like plasma exchange. This highlights the neuroinflammatory and neurodegenerative effects of PM2.5, which aligns with its ability to trigger systemic and CNS inflammation. The impact on EDSS scores at exacerbation and 90 days underlines the potential for PM2.5 to contribute to long-term disability," ” lead author Chutithep Teekaput, MD, an assistant professor in the department of internal medicine at Chiang Mai University in Thailand, told NeurologyLive^® in a recent interview. "From a clinical perspective, the exacerbation patterns in the study—peaking 2–4 months after air pollution events—imply a delayed effect of PM2.5 exposure on neuroinflammatory processes. Observations of increased relapses during pollution-heavy seasons might further support this linkage."

All told, patients aged 18 years or older who were diagnosed with MS or NMOSD according to respective clinical criteria, suspected of experiencing a clinical exacerbation, and admitted to the hospital were included in this analysis.^2,3 The primary outcome assessed was the EDSS score during exacerbation. Secondary outcomes included clinical measures, such as the change in EDSS before and after the exacerbation. Baseline data collected during initial exacerbations included patient demographics, medical history, disease status, laboratory findings, and neuroimaging results. Treatment outcomes evaluated included the use of intravenous methylprednisolone, plasma exchange, and the length of hospital stays.

READ MORE: Initiation of Maintenance Therapy After First Attack Improves Long-Term Relapse Risk, Disease Trajectory in MOGAD

Additional findings showed that the need for intensive treatments, such as plasma exchange, was notably higher in patients exposed to PM2.5. Moreover, these patients faced prolonged hospitalizations and more severe disease exacerbations compared with those without air pollution exposure. Authors noted that the radiological findings further corroborated the heightened impact of PM2.5 on disease severity.

Overall, these findings underscored the significant health impacts of PM2.5, which not only increased disease severity but also posed a risk of prolonged hospitalization and permanent disability. Notably, these effects were not observed with PM10 exposure. Authors noted that the highest incidence of exacerbations occurred 4 months after peak air pollution levels, which indicated a delayed but pronounced effect of fine PM.

“The study’s reliance on EDSS provides a robust measure of disability, but incorporating other tools like functional MRI or biomarkers (e.g., cytokine profiles) could enhance the understanding of subclinical neuroinflammation and the broader impact of air pollution on the CNS,” Teekaput noted in the interview. "The increased use of plasma exchange and prolonged hospital stays in PM2.5-exposed groups suggest a need for earlier intervention and closer monitoring of at-risk patients during pollution seasons. Steroid resistance and severe exacerbations might necessitate proactive adjustments in treatment protocols."

According to the authors, this study had several limitations. Air pollution data relied on ground-station measurements, highlighting the need for satellite-based data to enhance coverage and insights. The study population included significantly fewer MS cases compared to NMOSD, differing from distributions seen in Western populations. Prospective data collection may be needed for more robust trend analysis and associations. Furthermore, the study focused only on short-term PM2.5 and PM10 exposure, leaving long-term effects and the impact of other pollutants, such as sulfur dioxide, ozone, and nitrous gases, to be explored in future research.

"Given the findings, integrating air quality monitoring into clinical guidelines and promoting patient education on pollution avoidance are critical. Policymakers should address sources of PM2.5 (e.g., seasonal crop burning) and develop targeted interventions, especially in pollution-prone regions," Teekaput explained to NeurologyLive.

REFERENCES
1. Teekaput C, Rachbundit C, Wantaneeyawong C, Teekaput K, Thiankhaw K. Impact of air pollution on the clinical exacerbation of central demyelinating disease: A 10-year data from the Northern Thailand MS and NMOSD registry. Mult Scler Relat Disord. Published online January 10, 2025. doi:10.1016/j.msard.2025.106266
2. Thompson AJ, Banwell BL, Barkhof F, et al. Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria. Lancet Neurol. 2018;17(2):162-173. doi:10.1016/S1474-4422(17)30470-2
3. Wingerchuk DM, Banwell B, Bennett JL, et al. International consensus diagnostic criteria for neuromyelitis optica spectrum disorders. Neurology. 2015;85(2):177-189. doi:10.1212/WNL.0000000000001729