Air Pollution Worsens Outcomes in MS and NMOSD, Study Finds

Chutithep Teekaput, MD

(Credit: Bangkok Hospita)

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).

“Our study demonstrates a significant association between PM exposure and increased disability, as reflected by elevated EDSS from baseline at both exacerbation and 90-day follow-up. This suggests that PM exposure may contribute to inflammation and subsequent neurodegenerative processes,” lead author Chutithep Teekaput, MD, an assistant professor in the department of internal medicine at Chiang Mai University in Thailand, and colleagues noted.¹ “Undoubtedly, both PM2.5 and PM10 pose significant health risks in central demyelinating diseases, impacting not only individual health but also exerting a considerable strain on national budgets. The implementation of national policies addressing seasonal crop burning, traffic congestion, and industrial emissions is imperative.”

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.

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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.

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.

“The findings heighten the significance of disease control and monitoring before and during the peak duration of such pollution,” Teekaput, who also serves as a neurologist at Bangkok Hospital, et al noted.¹ “Furthermore, this emphasizes the urgent need for comprehensive policies to reduce PM exposure and underscores the importance of further research into the complex mechanisms linking air pollution to central demyelinating diseases together with other neurological disorders.”

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