Low levels of vitamin D doubles the risk of stroke in whites, but not in blacks, according to a new report by researchers at Johns Hopkins. Researchers say their findings back up evidence from earlier work at Johns Hopkins linking vitamin D deficiency to higher rates of death, heart disease and peripheral artery disease in adults.
The Hopkins team says its results fail to explain why African Americans, who are more likely to be vitamin D deficient due to their darker skin pigmentation’s ability to block the sun’s rays, also suffer from higher rates of stroke. Of the 176 study participants known to have died from stroke within a 14-year period, 116 were white and 60 were black. Still, African Americans had a 65% greater likelihood of suffering such a severe bleeding in or interruption of blood flow to the brain than whites, when age, other risk factors for stroke and vitamin D deficiency were factored into their analysis.
“Higher numbers for hypertension and diabetes definitely explain some of the excess risk for stroke in blacks compared to whites, but not this much risk,” study co-lead investigator and preventive cardiologist Erin Michos, MD, MHS, an assistant professor at the Johns Hopkins University School of Medicine and its Heart and Vascular Institute, stated in a press release.
Nearly 8,000 initially healthy men and women of both races were involved in the latest analysis, part of a larger, ongoing national health survey, in which the researchers compared the risk of death from stroke between those with the lowest blood levels of vitamin D to those with higher amounts. Among them, 6.6% of whites and 32.3% of blacks had severely low blood levels of vitamin D, which the experts say is less than 15 nanograms per milliliter.
“It may be that blacks have adapted over the generations to vitamin D deficiency, so we are not going to see any compounding effects with stroke,” Michos, who notes that African Americans have adapted elsewhere to low levels of the bone-strengthening vitamin, with fewer incidents of bone fracture and greater overall bone density than seen in Caucasians, stated. “In blacks, we may not need to raise vitamin D levels to the same level as in whites to minimize their risk of stroke.”