Neurology. 2013 May 7;80(19):1734-9. doi: 10.1212/WNL.0b013e3182918cc2.
Langer-Gould A, Brara SM, Beaber BE, Zhang JL.
From the Department of Research and Evaluation (A.L.-G., J.L.Z.), Kaiser Permanente, Southern California, Pasadena; and Neurology Department (A.L.-G., S.M.B., B.E.B.), Kaiser Permanente, Southern California Los Angeles Medical Center, CA.
OBJECTIVE: To determine whether the incidence of multiple sclerosis (MS) varies by race/ethnicity in a multiethnic, population-based cohort.
METHODS: We conducted a retrospective cohort study of more than 9 million person-years of observation from the multiethnic, community-dwelling members of Kaiser Permanente Southern California health plan from January 1, 2008 to December 31, 2010. Incidence of MS and risk ratios comparing incidence rates between racial/ethnic groups were calculated using Poisson regression.
RESULTS: We identified 496 patients newly diagnosed with MS who met McDonald criteria. The average age at diagnosis was 41.6 years (range 8.6-78.3 years) and 70.2% were women. The female preponderance was more pronounced among black (79.3%) than white, Hispanic, and Asian individuals with MS (67.8%, 68.1%, and 69.2%, respectively; p = 0.03).
The incidence of MS was higher in
- blacks (10.2, 95% confidence interval CI 8.4-12.4; p < 0.0001) and lower in
- Hispanics (2.9, 95% CI 2.4-3.5; p < 0.0001) and
- Asians (1.4, 95% CI 0.7-2.4; p < 0.0001) than
- whites (6.9, 95% CI 6.1-7.8).
Black women had a higher risk of MS (risk ratio 1.59, 95% CI 1.27-1.99; p = 0.0005) whereas black men had a similar risk of MS (risk ratio 1.04, 95% CI = 0.67-1.57) compared with whites.
CONCLUSIONS: Our findings do not support the widely accepted assertion that blacks have a lower risk of MS than whites. A possible explanation for our findings is that people with darker skin tones have lower vitamin D levels and thereby an increased risk of MS, but this would not explain why Hispanics and Asians have a lower risk of MS than whites or why the higher risk of MS among blacks was found only among women.
Perhaps because black women have lower levels of vitamin D than black men.