According to a study published in the journal Neurology, environmental factors play a greater part in the development of multiple sclerosis than was previously thought.
Researchers from Copenhagen University found that those who spent time in the sun every day during the summer as teenagers developed the disease later than those who said they did not spend time in the sun every day.
The study also reports that people who were overweight by the age of 20 developed the disease earlier than those who were average weight or underweight.
The study’s author Julie Hejgaard Laursen said:
‘The factors that lead to developing MS are complex and we are still working to understand them all, but several studies have shown that vitamin D and sun exposure may have a protective effect on developing the disease. This study suggests that sun exposure during the teenage years may even affect the age at onset of the disease.’
During the study over 1,000 people with multiple sclerosis filled out questionnaires and gave blood samples. They were separated into two groups based on sun exposure, and asked about their use of vitamin D supplements and dietary habits.
The average onset of MS was almost two years later for those who spent more time in the sun in their youth. Participants in this group developed MS at an average age of 32.9, compared to 31 for those who were not in the sun every day.
When the volunteers were categorised according to their weight at the age of 20, the researchers found that those who were overweight developed the disease on average 1.6 years earlier than those who weren’t.
‘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. 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.’