Onset of multiple sclerosis, an unpredictable disease of the central nervous system, could be delayed by spending more time in the sun during the teenage years, according to research published in the journal Neurology.
According to the National Institute of Neurological Disorders and Stroke (NINDS), there may currently be 250,000-350,000 people in the US with multiple sclerosis (MS), with approximately 200 new cases diagnosed every week.
Symptoms can range from mild to devastating, as communication between the brain and other parts of the body is disrupted. The first sign is usually blurred or double vision. People with MS often experience muscle weakness in their extremities and difficulty with coordination and balance.
The majority are mildly affected, but MS can cause paralysis, leaving a person unable to write, speak or walk. Most people experience their first symptoms of MS between the ages of 20 and 40. As yet, there is no cure.
Previous research has linked risk of MS with obesity in childhood and adolescence. Obesity is also associated with low levels of vitamin D.
A team from Copenhagen University Hospital in Denmark set out to investigate a link between MS, obesity and vitamin D levels in the teenage years.
Time spent in the sun delayed onset of MS
The participants were 1,161 people with MS in Denmark who completed a questionnaire and gave blood samples. They were divided into two groups, based on their sun habits during their teenage years: those who spent time in the sun every day, and those who did not. They were also asked about their use of vitamin D supplements during their teenage years and how much fatty fish they ate at age 20.
A total of 88% of the participants spent time in the sun every day as teens, and they developed the disease later than those who did not spend time in the sun every day.
The average onset age of those who spent time in the sun every day was 1.9 years later than those who did not. Those who spent time in the sun developed MS at an average age of 32.9, compared with 31 for those who were not in the sun every day.
Obesity may cause early development of disease
In addition, people who were overweight at age 20 developed the disease earlier than those who were average weight or underweight.
Those who were overweight at age 20 developed the disease an average of 1.6 years earlier than those of average weight, and 3.1 years earlier than those who were underweight. Of the participants, 18% were overweight; they developed the disease at an average age of 31.2 years.
Dr. Julie Hejgaard Laursen, PhD, lead author of the study, says:
“The relationship between weight and MS might be explained by a vitamin D deficiency, but there’s not enough direct evidence to establish this yet. It appears that both UVB rays from sunlight and vitamin D could be associated with a delayed onset of MS. However, it’s possible that other outdoor factors play a role, and these still have to be identified.”
She adds that the factors leading to MS are complex and still not well understood.
However, like other studies, this research supports the view that vitamin D and sun exposure may offer some protection against the development of MS, and that during the teenage years, it may even delay the start of the disease.
One limitation of the study is that participants were asked to remember their sun, eating and supplement habits from years before, which could lead to errors in recall, especially if a participant had developed the disease a long time ago. Additionally, only Danish patients were surveyed; the results could be different for other ethnicities and geographical locations.
Earlier this year, Medical News Today published findings of another study linking MS with low levels of vitamin D.
Written by Yvette Brazier