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People with multiple sclerosis (MS) who are less socioeconomically advantaged tend to have faster rates of nervous system damage, new research suggests.
The findings were presented today at the virtual Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2021, in the presentation “Socioeconomic Disparity Correlates with Faster GCIPL Atrophy in MS Patients,” given by Eleni Vasileiou, MD. Vasileiou is a postdoctoral researcher at Johns Hopkins University School of Medicine, Baltimore, Maryland.
Socioeconomic status has profound effects on health outcomes. For example, previous research has demonstrated that less socioeconomically advantaged MS patients tend to have greater disability. However, the relationship between socioeconomic status and nervous system damage in MS has been less clear.
To shed light on this relationship, Vasileiou and colleagues analyzed data from 789 people with MS, followed at the Johns Hopkins Multiple Sclerosis Center. All patients had nine-digit ZIP codes and optical coherence tomography (OCT) data available within a period of 10 years of their MS diagnosis.
OCT is an imaging technique that allows the assessment of the optic nerves that connect the eye to the brain. From OCT measurements, investigators calculated the rate of decline in the longitudinal thickness of the ganglion cell plus inner plexiform layer (GCIPL), a surrogate for brain atrophy (shrinkage) and disability accumulation.
The ZIP codes were used as a proxy for measuring socioeconomic status, including the median household income and area of deprivation index, which is a composite measure that takes into account several indicators, including income, poverty, employment and housing quality. Patients’ education levels also were assessed.
In their study, the team defined socioeconomic status as “a combination of financial, educational and occupational influences that directly interacts with individual health,” Vasileiou said. Generally, socioeconomic status was assessed based on quartiles, i.e., comparing the top 25% to the bottom 25%.
“The ultimate question we aimed to address is: is socioeconomic status a predictor of disease progression in MS?” Vasileiou said.
Of note, in the patient group analyzed, the most socioeconomically disadvantaged quartile, compared to the most privileged quartile, included a higher percentage of African Americans (37.6% vs. 8.7% in the least disadvantaged quartile) and women (79% vs. 68.9%), which is generally consistent with known race- and gender-based socioeconomic disparities in the U.S. population.
The most socioeconomically disadvantaged quartile also had a higher percentage of obesity: 42.9% vs. 22.4% in the least disadvantaged quartile.
Overall, results showed that MS patients of lower socioeconomic status — at both state and national levels — had a significantly faster GCIPL atrophy rate, indicating more rapid damage to the nervous system.
Specifically, based on state-level data, those in the most disadvantaged quartile experienced a rate of decline of 0.12 micrometers per year faster compared to the least disadvantaged quartile. Based on national data, the rate of decline was 0.08 micrometer/year faster in the most disadvantaged quartile. Based on median household income, the difference was of 0.08 micrometer/year.
MS patients with more education (generally tied to richer socioeconomic status) had a significantly slower rate of decline in GCIPL, with the most- educated quartile experiencing a 0.18 micrometer/year slower rate of decline, compared to the least-educated quartile.
Low socioeconomic status also was associated with an increased risk of new onset comorbidities (additional health problems), including hypertension, depression, diabetes, migraine, coronary artery disease, and osteoporosis, among others.
“Disadvantaged people had almost twofold increased risk of developing any comorbidities, when compared to more privileged participants,” Vasileiou said.
Vasileiou noted, however, that these findings could be due to reverse causation, meaning it is possible that people with more severe MS are more likely to experience socioeconomic hardship as a result of their disease. To account for this possibility, the team conducted a separate analysis using only data from closer to the time of diagnosis — within three years of MS onset, rather than 10 years (a total of 522 patients).
“What we saw was the exact same thing: more disadvantaged participants exhibited higher rates of GCIPL atrophy,” Vasileiou said, suggesting that reverse causation would not account for these findings.
Another possible explanation for this difference is that individuals of lower socioeconomic status are given less effective treatments. However, the researchers found that people who were more disadvantaged actually were more prone to therapeutic escalation — that is, switching from a lower-efficacy medication to a higher-efficacy medication.
Specifically, the time to therapeutic escalation was about 33% faster among more disadvantaged people. This indicates that differences in treatment efficacy do not account for the differences in GCIPL decline based on socioeconomic status.
“In this analysis, we found evidence that socioeconomic disparity was independently associated with [an] increased rate of [GCIPL] atrophy. More socioeconomically disadvantaged individuals were also [at] higher risk of faster disease progression despite being on a higher efficacy treatment. Also, more disadvantaged individuals had a higher propensity of developing a new comorbidity during follow-up,” Vasileiou said.
Collectively, the findings highlight the need for better strategies to help socioeconomically disadvantaged people with MS.
“Since we have evidence that socioeconomic status may play a role in disease prognosis, implementing more efficient comorbidity prevention and management strategies, as well as [therapeutic approaches] may help limit the gap and the inequality in disease progression across the [socioeconomic] gradient,” Vasileiou concluded.
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