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Impact of paramagnetic rim lesions on disability and race in multiple sclerosis: mediation analysis
Nara M Michaelson1, Sandra H Rúa2, Ulrike W Kaunzner1
1Department of Neurology, Weill Cornell Medicine, New York, New York, USA.
Objective:
Black American (BA) multiple sclerosis (MS) patients experience greater disability compared to White American (WA) patients. Here, we investigated the role of paramagnetic rim lesions (PRLs), a subset of chronic active lesions, on race-related disability in MS.
Methods:
We conducted a retrospective observational study comparing BA and WA MS patients. PRLs were identified through Quantitative Susceptibility Mapping (QSM) MRI. A causal mediation analysis explored the impact of PRLs on the relationship between race and disability, as measured by the Expanded Disability Status Scale (EDSS).
Results:
The prevalence of PRLs in BA patients with MS was higher at 55% compared to WA patients at 39% (p = 0.022). A higher percentage of PRLs among all white matter lesions was observed with BA (8.01%) patients compared to WA (3.4%) patients (p = 0.003). In a regression analysis, controlling for significant patient-level covariates and income-level demographics, the percentage of PRLs was, on average, 4.61 points higher for BA patients than for WA patients (p = 0.003). In a separate regression analysis, accounting for covariates, BA patients exhibited significantly higher EDSS scores (p < 0.001). Further analysis demonstrated that the percentage of PRLs was a mediator in the association between BA patients and greater disability (p = 0.031). Higher proportion of PRLs in BA population accounted for 14% of the total effect of race on disability.
Interpretation:
BA patients exhibit greater disability, in part, due to their higher proportion of PRLs. This study underscores the substantial impact of chronic active lesions on disability outcomes in this specific minority MS patient population.
Insights
Black American multiple sclerosis (MS) patients have more severe disability, partly because they have a higher proportion of paramagnetic rim lesions (PRLs). These chronic active lesions significantly impact disability outcomes in this population.
Area of Science:
- Neurology
- Radiology
- Immunology
Background:
- Multiple sclerosis (MS) disproportionately affects Black American (BA) patients, who experience greater disability compared to White American (WA) patients.
- The underlying reasons for this race-related disparity in MS disability remain incompletely understood.
Purpose of the Study:
- To investigate the role of paramagnetic rim lesions (PRLs), a marker of chronic active lesions, in the increased disability observed in Black American MS patients.
- To explore PRLs as a potential mediator of the relationship between race and MS disability.
Main Methods:
- Retrospective observational study comparing BA and WA MS patients.
- Identification of PRLs using Quantitative Susceptibility Mapping (QSM) MRI.
- Causal mediation analysis to assess the impact of PRLs on race-related disability (Expanded Disability Status Scale - EDSS).
Main Results:
- PRLs were more prevalent in BA MS patients (55%) than WA MS patients (39%).
- A higher percentage of white matter lesions were PRLs in BA patients (8.01%) compared to WA patients (3.4%).
- PRLs mediated 14% of the association between being BA and experiencing greater MS disability, even after controlling for covariates.
Conclusions:
- Black American MS patients experience greater disability, with a higher proportion of paramagnetic rim lesions contributing significantly to this disparity.
- This finding highlights the critical role of chronic active lesions, specifically PRLs, in driving disability outcomes in minority MS populations.
