Vitamin D deficiency may be a risk factor for the development of multiple sclerosis (MS), according to Finnish researchers who published their results in the most recent issue of the journal Neurology. They noted that measuring these levels in the blood may help predict which individuals are at higher risk. They added that these results provide the basis for developing broad public health interventions to improve vitamin D levels in women.
“There have only been a few small studies suggesting that levels of vitamin D in the blood can predict risk,” said study author Kassandra Munger, ScD, of the Harvard T.H. Chan School of Public Health in Boston. “Our study, involving a large number of women, suggests that correcting vitamin D deficiency in young and middle-age women may reduce their future risk of [developing] MS.”
For this prospective, nested, case-control study, Dr. Munger and colleagues included women from the Finnish Maternity Cohort (FMC), which has 1.8 million stored serum samples taken during the pregnancies of over 800,000 women.
They identified 1,092 women with MS, who had been diagnosed between 1983 and 2009, with at least one serum sample collected before the date of their MS diagnosis. In 511 cases, two or more serum samples were available.
Researchers then matched cases with up to 3 controls (n=2,123) by date of birth and area of residence. Using a chemiluminescence assay, they measured 25-Hydroxyvitamin D (25[OH]D) levels, and used conditional logistic regression adjusted for sample year, gravidity, and parity to determine the relative risks and 95% confidence intervals.
They found that a 50 nmol/L increase in 25(OH)D was associated with a 39% reduction in risk of MS (RR: 0.61; 95% CI: 0.44, 0.85; P=0.003). Compared with women with 25(OH)D levels ≥ 50 nmol/L, women with < 30 nmol/L had a 43% higher risk of developing MS (RR: 1.43; 95% CI: 1.02, 1.99; P=0.04).
Among women who provided two or more samples, researchers found that the MS risk was 2-fold higher in those with 25(OH)D < 30 nmol/L, compared with women with levels ≥ 50 nmol/L (RR: 2.02; 95% CI: 1.18, 3.45; P=0.01).
“More research is needed on the optimal dose of vitamin D for reducing risk of MS. But striving to achieve vitamin D sufficiency over the course of a person’s life will likely have multiple health benefits,” concluded Dr. Munger.
She added a few caveats, however, to these results. One possible limitation of the study may be that subjects were primarily white women, and another was that although serum samples were obtained an average of 9 years before diagnosis of MS, some women may have already had MS at the time of sampling without yet being symptomatic.
This study was supported by the National Institute of Neurological Disorders and Stroke.