A new study by the University of California San Francisco and the Australian National University shows that children and young adults exposed to the Sun may protect from multiple sclerosis diagnosis (MS).
The study follows previous work by other researchers that have demonstrated an association between increased ultraviolet exposure in childhood and lower odds of multiple sclerosis diagnosis later in life.
The new study was published in an online issue of Neurology, the journal of the American Academy of Neurology.
Multiple sclerosis diagnosis and Sun exposure
The study involved 332 participants aged between three to 22 who had a multiple sclerosis diagnosis for an average of seven months. Their locations and amount of Sun exposure were matched by age and sex to 534 participants without MS.
Questionnaires were filled in by participants with a multiple sclerosis diagnosis or their parents; 19% stated that they spent less than 30 minutes daily outdoors during the previous summer, compared to 6% of those who did not have MS. When the researchers adjusted for MS risks, like smoking and female sex, they found that the participants who spent an average of 30 minutes to one hour outdoors daily had a 52% lower chance of a multiple sclerosis diagnosis, compared to those who spent an average of fewer than 30 minutes outdoors.
“Sun exposure is known to boost vitamin D levels,” said co-senior author Emmanuelle Waubant, MD, PhD, professor in the UCSF Department of Neurology and of the Weill Institute for Neurosciences. “It also stimulates immune cells in the skin that have a protective role in diseases such as MS. Vitamin D may also change the biological function of the immune cells and, as such, play a role in protecting against autoimmune diseases.”
An estimated 2.5m people live with MS
Multiple sclerosis (MS) is an autoimmune disease that affects around 2.5 million people worldwide. Paediatric-onset MS is initially highly inflammatory, but it takes longer for the autoimmune disease to advance in adults. Symptoms of secondary progression include moderate to severe weakness, poor coordination and bowel and bladder control and occur on average 28 years after disease onset, according to experts. However, these disability landmarks are reached approximately ten years earlier than in adult MS.
The researchers also found an association with the intensity of sunlight and estimated that residents of Florida would be 21% less likely than residents of New York to have MS. They noted that Sun exposure was “dose-dependent,” the longer the exposure, the lower the risk. Furthermore, exposure in the first year of life appeared to protect against MS.
Fortunately, using Sun cream does not appear to reduce the therapeutic effects of sunlight in warding of multiple sclerosis diagnosis. Clinical trials are needed to determine if “increasing Sun exposure or vitamin D supplementation can prevent the development of MS or alter disease course post-diagnosis,” commented Waubant. Meanwhile, “advising regular time in the Sun of at least 30 minutes daily especially during summer, using Sun protection as needed, especially for first degree relatives of MS patients, maybe a worthwhile intervention to reduce the incidence of MS.”
Limited Sun exposure and/or low levels of vitamin D have been associated with other conditions. These include Parkinson’s disease, Alzheimer’s and other types of dementia, schizophrenia, and other autoimmune diseases like Type 1 diabetes, Crohn’s disease, and lupus.
