Black women have higher incidence of multiple sclerosis than White women

Multiple sclerosis is more common in Black women than in White women, according to a Kaiser Permanente study conducted in Southern California and published today in the journal Neurology.

The findings run contrary to the widely accepted belief that Blacks are less susceptible to MS, according to the researchers, who examined the electronic health records of more than 3.5 million members of Kaiser Permanente Southern California between January 2008 and December 2011 and identified 496 people newly diagnosed with MS.

Of those diagnosed cases, Black patients had a 47 percent higher risk of MS than White patients, while Hispanic and Asian patients had a 50 percent and 80 percent lower risk, respectively, compared to White patients.

The study also found that 70 percent of MS diagnosed cases occurred in females, a preponderance more pronounced among Black patients than White patients.

The researchers also found that Black women had a higher incidence of MS than White patients of both genders, while Black men had a similar risk of being diagnosed with MS compared to White men. The lower risk among Hispanic and Asian patients was true for both sexes.

“Our findings do not support the widely held belief that Blacks have a lower risk of MS than whites, but that MS risk is determined by complex interactions between race, ethnicity, sex, environmental factors and genotypes,” said the study’s lead author, Dr. Annette Langer-Gould of the Pasadena-based Kaiser Permanente Southern California Department of Research Evaluation.

Additional research is needed, but possible explanations for the higher incidence of MS in Black women include a greater prevalence of hormonal, genetic or environmental risk factors such as smoking, compared to patients from other racial or ethnic groups, she said.

The study estimates 19,000 people per year — or 250 per week — are newly diagnosed with MS in the United States. The researchers put the average age of MS diagnosis at 41.6 years, but found onset occurred anywhere between 8.6 and 78.3 years among the study participants.

The study also found the median time from symptom onset to MS diagnosis was four months, but could be as long as 40 years. Hispanic and Asian patients were generally younger at the time of MS diagnosis than white and Black patients, the researchers found.

According to the researchers, the belief that MS is rare in Blacks is based on worldwide prevalence studies and a single study of Korean War veterans in the 1950s, which found white men were twice as likely to receive disability compensation for MS as Black men.

“A possible explanation for our findings is that people with darker skin tones have lower vitamin D levels and therefore an increased risk of MS. However, this does not explain why Hispanics and Asians have a lower risk of MS than Whites, or why only Black women but not Black men are at a higher risk of MS,” Langer-Gould said.

“Our findings indicate that including persons from different racial and ethnic groups in future studies of MS susceptibility and prognosis will likely reveal important insights into the causes of this often debilitating disease,” she siad.

MS attacks the central nervous system, which is made up of the brain, spinal cord and optic nerves. Symptoms may be mild, such as numbness in the limbs, or severe, such as paralysis or loss of vision.

The progress, severity and specific symptoms of the chronic disease are unpredictable and vary from one person to another.

Because the Centers for Disease Control and Prevention does not require U.S. physicians to report new cases of MS and symptoms can be invisible, the prevalence of the disease in this country can only be estimated.

An earlier Kaiser Permanente study published in the journal Neurology found obesity in teenage girls was associated with an increased risk of developing MS.

Researchers are currently recruiting patients for a study to examine the complex interactions between MS risk factors such as sunshine, low vitamin D, skin tone, infections, other environmental and genetic factors across racial/ethnic groups. Researchers expect to release findings of that study in 2015.

Tagged African American Women, Asian, Black Men, Black Women, brain, environmental factors, ethnicity, genotypes, Hispanic, Kaiser Permanente Southern California, Latina Women, Multiple sclerosis, optic nerves, race, sex, spinal cord, Vitamin D, White Women