the studies show that geography plays an important role in getting Multiple Sclerosis. for example the percentage of the people suffering from MS is higher in Northern European countries.
Studies indicates that low vitamin D levels in regions with less sunshine exposure may be the reason behind increased incidence of multiple sclerosis (MS).
Please also have a look at these useful RG links and PDF attachments.
Article Multiple Sclerosis in Cyprus: A Fourteen Year (2000-2014) Ep...
Article Multiple sclerosis: New insights and trends
A 1986 paper by Sharpe (Med Hypotheses) suggests that low incidence of multiple sclerosis near the equator is due to ultraviolet light induced suppressor cells to melanocyte antigens. Other theories may also be out there.