A new study by Swedish researchers has reported that individuals with high levels of Vitamin D in their blood have a lower risk of developing multiple sclerosis (MS). Researchers affiliated with Umeå University, Umeå, Sweden published their findings on November 20 in the journal Neurology.
The goal of the study was to examine the association between Vitamin D (25-hydroxyvitamin D (25[OH]D)) levels and the risk of MS in blood samples collected prospectively and during pregnancy. (Prospective collection means that the samples were collected before the individuals developed MS.) The investigators evaluated 291,500 blood samples from 164,000 individuals collected since 1975 in the northern half of Sweden. They identified prospectively collected blood samples from 192 MS cases matched two to one with controls matched and samples from pregnant mothers whose offspring had later developed MS (37 women, matched five to one with controls. Vitamin D levels were measured using an ELISA, and the risk of MS was analyzed using matched logistic regression.
The researchers found that Vitamin D levels in prospectively collected blood samples were associated with a decreased risk of MS (odds ratio: 0.39). No decrease in MS risk was found in the offspring exposed to higher Vitamin D levels in utero. The prevalence of Vitamin D levels in the control women decreased gradually from 1976 through 2005.
The researchers concluded that their study supports the presence of an association between high Vitamin D levels during the years preceding disease onset and a decreased risk of MS. In the very limited material with samples drawn in early pregnancy, where month-of-birth effects were controlled for, they found no association between gestational Vitamin D levels and MS risk in the offspring. They noted that decreasing Vitamin D levels in the population may contribute to explain the increasing MS incidence that is suggested from epidemiologic studies.
MS affects woman more than men. The disorder most commonly begins between ages 20 and 40, but can be seen at any age. It is caused by damage to the myelin sheath, the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve impulses are slowed down or stopped. MS is a progressive disease, meaning the nerve damage (neurodegeneration) gets worse over time. How quickly MS gets worse varies from person to person.
The nerve damage is caused by inflammation. Inflammation occurs when the body's own immune cells attack the nervous system. Repeated episodes of inflammation can occur along any area of the brain and spinal cord. Researchers are not sure what triggers the inflammation. The most common theories point to a virus or genetic defect, or a combination of both. MS is more likely to occur in northern Europe, the northern United States, southern Australia, and New Zealand than in other areas. Geographic studies indicate there may be an environmental factor involved. People with a family history of MS and those who live in a geographical area with a higher incidence rate for MS have a higher risk of the disease.
Symptoms vary, because the location and severity of each attack can be different. Episodes can last for days, weeks, or months. These episodes alternate with periods of reduced or no symptoms (remissions). Fever, hot baths, sun exposure, and stress can trigger or worsen attacks. It is common for the disease to return (relapse). However, the disease may continue to get worse without periods of remission. Because nerves in any part of the brain or spinal cord may be damaged, patients with multiple sclerosis can have symptoms in many parts of the body.