Racial Differences Detected Regarding Impact of Obesity on Retinal Integrity in MS

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Obesity was found to have a significant association with retinal structure abnormalities related to multiple sclerosis (MS); however, the impact may be greater for African Americans than Caucasian Americans.

The observational research study, published in Frontiers in Neurology, demonstrated the impact of elevated body mass index (BMI) on the peripapillary retinal nerve fiber layer (pRNFL), inner nuclear layer (INL), and retinal nerve fiber layer (RNFL) of the eye in patients with relapsing-remitting MS (RRMS), as well as the more severe impact that obesity has on African Americans.

“Our findings should be considered preliminary but encouraging, and they should support efforts to further extend these observations to a larger cohort of patients with MS. Should our findings be confirmed in larger longitudinal studies, BMI monitoring and maintenance of a healthy weight would have an important impact on the improvement of care of patients with MS,” wrote the investigators.

Imaging measures can be used to detect RRMS, including optical coherence tomography (OCT), which is a noninvasive method for measuring retinal morphology and quantifying RNFL. Reduced RNFL is associated with disease progression, and obesity is known to contribute to persistent low-grade inflammation of the central nervous system.

Although some studies have found promising biomarkers, definitive findings that obesity has an impact on MS disease progression have not been determined and there has been little research about whether MS disease progression and its biomarkers are different across racial groups.

The investigators conducted the study between March 2016 and December 2018, during which they collected data on patients’ weight and height to determine their BMI and OCT scans performed at their clinic.

Overall, 136 patients were enrolled in the study and were classified as either obese (BMI > 30; n = 67) or nonobese (BMI < 30; n = 69). In the obese group, 51 were women, 40 were African American, and 27 were Caucasian. In the nonobese group, there were 42 women, 23 African Americans, and 46 Caucasians. There were nonsignificant differences in age and disease duration between the BMI groups.

The investigators found that the temporal quadrant thickness of the pRNFL (P = .044) and the RNFL volume (P = .009) were significantly lower in the obese group compared with the nonobese group. In addition, the INL volume was observed to be significantly higher in the obese group (P = .034).

Within the obese group, the thickness of the temporal (P = .033) and nasal (P = .044) of the pRNFL quadrants were significantly lower among those who were African American compared with patients who were Caucasian.

Several of the macular layers were also found to be significantly less among African American patients than Caucasian patients in the obese group, including total macular volume (P = .003), RNFL (P = .013), outer plexiform layer (P = .050), outer nuclear layer (P = 0.026), and ganglion cell and inner plexiform layer (P = .038). An intraracial analysis was significant between obese and nonobese African American patients for the temporal quadrant of pRNFL (P = .05).

The lack of a healthy control group, omission of an overweight classification, and use of BMI as a measurement of body fat despite often varying by sex, age, and race were all listed as study limitations. The investigators said that larger longitudinal studies are needed to validate their findings.

“Given that obesity rates have nearly doubled since 1980, continuing to monitor obesity in clinical populations and its effects on comorbid diseases is becoming increasingly relevant,” they wrote.

Reference

Rube J, Bross M, Bernitsas C, Hackett M, Bao F, Bernitsas E. Effect of obesity on retinal integrity in African Americans and Caucasian Americans with relapsing multiple sclerosis. Front Neurol. Published online November 24, 2021. doi:10.3389/fneur.2021.743592