June 10, 2010 (San Antonio, Texas) — Levels of childhood sun exposure and the presence or absence of cod liver oil supplements predict age at onset of multiple sclerosis (MS), a new study suggests.
"There's been demonstrated to be a north–south gradient in multiple sclerosis incidence, and migrating later on in life, even after a diagnosis of MS, from a colder to a warmer climate, has been associated with an improvement in disease course," Walter Royal, III, MD, associate director for research at the Veterans Affairs MS Center of Excellence, East, Baltimore, MD, who presented the work here at the Consortium of Multiple Sclerosis Centers 24th Annual Conference and the Third Joint Meeting of Americas Committee for Treatment and Research in Multiple Sclerosis, told Medscape Neurology.
Vitamin D is known to affect immune system functions that appear to benefit MS and other autoimmune diseases. The new research further demonstrates that "early experience can have a lasting effect," Dr. Royal added.
Reduced MS Risk
Previous studies have shown that childhood sun exposure and cod liver oil supplements are associated with reduced risk of developing MS. In this report, the researchers examined a national cohort of veterans to determine whether these environmental factors affected the timing of symptom onset.
Participants were recruited from the nationally representative Veterans Health Administration Multiple Sclerosis Surveillance Registry, which includes age at MS symptom onset, disease subtype, home address location history, sun exposure, and intake of high vitamin D–content foods. All information was available by 5-year increments.
For each participant, the researchers estimated past sun exposures for fall/winter and spring/summer seasons. They used latitude, altitude, and ultraviolet radiation count of the reported home residences to estimate solar radiation exposure. Multiple regression analysis was then used to link these variables to age at MS onset. The study included 948 patients with relapsing MS.
For those living in low– to medium–solar radiation areas, the researchers found a significant association between earlier age at onset of symptoms and sun exposure in the fall/winter season between the ages of 6 and 15 years (2.3 years average earlier onset; P = .01). Intake of cod liver oil during childhood produced a 3-year delay in onset (P = .01).
Vitamin D levels are frequently low in patients with MS, and physicians often prescribe supplements. The results of this study imply that such the strategy should be successful in changing the course of the disease, and that children of patients with MS should receive vitamin D supplements, according to Dr. Royal.
Time in the Sun
However, given the concerns today about sun exposure, many children are encouraged to spend less time in the sun, or to wear skin protection when they do. MS also has a relatively low family incidence, so identifying at-risk children is difficult, according to James Simsarian, MD, director of the Multiple Sclerosis Program at the Neurology Center of Fairfax, Virginia, who attended the session here.
"We've always talked about environmental factors at play [in developing MS], and [vitamin D exposure] could be one of them," Dr. Simsarian told Medscape Neurology.
The study did not receive commercial support. Dr. Prieto and Dr. Schapiro have disclosed no relevant financial relationships.
Consortium of Multiple Sclerosis Centers (CMSC) 24th Annual Conference and the Third Joint Meeting of Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS): Abstract S89. Presented June 4, 2010.
Medscape Medical News © 2010
Cite this: Vitamin D Exposure in Childhood Linked to Age at Onset of MS - Medscape - Jun 10, 2010.