Racial and Ethnic Disparities in Multiple Sclerosis Prevalence

Abstract

Background and objectives: The goal of this work was to determine whether the prevalence of multiple sclerosis (MS) varies by race and ethnicity.

Methods: We conducted a retrospective cohort study of >2.6 million adults from the multiethnic, community-dwelling members of Kaiser Permanente Southern California. The complete electronic health records of individuals with at least 1 ICD-9 code for MS between January 1, 2008 and December 31, 2010 were reviewed. MS prevalence and 95% CIs stratified by age, sex, and race and ethnicity among 2010 members were estimated with binomial regression. Age- and sex-standardized prevalence was estimated according to the 2010 US Census population.

Results: We identified 3,863 patients with MS. The average age of patients with prevalent MS was 51.7 years (SD 13.1 years), and 76.8% were women. The female preponderance was more pronounced among Black (81.2%) and Asian (83.6%) than White (76.3%) or Hispanic (74.5%) individuals with MS. Age- and sex-standardized MS prevalence per 100,000 was similarly high among Black (225.8, 95% CI 207.1-244.5) and White (237.7, 95% CI 228.2-247.2) and significantly lower among Hispanic (69.9, 95% CI 64.4-75.5) and Asian (22.6, 95% CI 17.1-28.1) persons. MS prevalence was highest between the ages of 35 and 64 years and declined after 65 years of age across all racial and ethnic groups. Among adults 18 to 24 years of age, the crude MS prevalence was low but was highest among Black and Hispanic young adults, lower in White people, and lowest in Asian/Pacific Islander individuals (48.5, 25.0, 18.0, and 7.1 per 100,000, respectively).

Discussion: MS prevalence varies by race and ethnicity, being similarly high in White and Black and significantly lower in Hispanic and Asian persons in Southern California. Taken together with previous studies, these findings indicate that the burden of MS in the US Black community has long been underrecognized. More studies are needed to determine whether MS is an emerging disease among US Hispanic adults and whether MS susceptibility and prevalence vary among Hispanic or Asian individuals from different cultures or ancestral backgrounds.

Figure 1. MS Prevalence by Race and Ethnicity in Southern California

Prevalence (indicated by the number above each bar in B) and 95% CIs of multiple sclerosis (MS) in White (blue), Black (black), Hispanic (green), and Asian/Pacific Islander (API) (orange) individuals residing in Southern California by age groups by years (A) and sex (B). MS prevalence is highest in White and Black persons, lower in Hispanic individuals, and lowest in the heterogeneous group of Asian/Pacific Islander persons residing in Southern California across all age groups except 18- to 24-year-olds, for whom the prevalence in Hispanic persons is similar to that in White and highest in Black persons. MS prevalence continues to increase with age in White persons through 55 to 64 years of age, whereas in Black persons, MS prevalence rises until 35 to 44 years of age and then remains stable through 55 to 64 years of age. MS prevalence declines in the ≥65-year-old age groups across all racial and ethnic groups. MS prevalence is similar in Black and White persons in both women (crude risk ratio [RR] 0.93, 95% CI 0.84–1.03, p = 0.17, Poisson regression with White persons as the reference group) and men (crude RR 0.91, 95% CI 0.75–1.02, p = 0.39, Poisson regression with White persons as the reference group). MS prevalence is lower in Hispanic and Asian/Pacific Islander compared to White persons, regardless of sex. MS prevalence is higher in women compared to men across all racial and ethnic groups (White individuals: crude RR 3.09, 95% CI 2.82–3.39, p < 0.0001; Black individuals: crude RR 3.15, 95% CI 2.56–3.88, p < 0.0001; Hispanic individuals: crude RR 2.66, 95% CI 2.23–3.17, p < 0.0001; Asian/Pacific Islander individuals: crude RR 4.12, 95% CI 2.16–7.87, p < 0.0001).

Figure 2. MS Sex- and Age-Specific Prevalence by Race and Ethnicity in Southern California

Crude sex- and age-specific prevalence of multiple sclerosis (MS) and 95% CIs among White persons (A), Black persons (B), Hispanic persons (C), and the heterogeneous group of Asian/Pacific Islander persons (A/PI; D) residing in Southern California. The female predominance and peak prevalence between 35 and 64 years of age are remarkably similar between White and Black persons. While this pattern is similar in Hispanic persons, the magnitude of increase among Hispanic women and men is significantly lower than for Black or White persons. Among Asian women, prevalence increased from ages 18 to 24 years to 25 to 34 years but no longer after that. MS prevalence was very low among Asian men in all age groups.