A new study has found a significant negative correlation between sunlight exposure and multiple sclerosis (MS) among residents of Italy and Norway, with the strongest negative correlation between living in Italy during early childhood and living in Norway during late adolescence. Study author Kjetil Lauvland Bjørnevik presented the new study data at the 28th European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) Congress. He noted that the results of the study suggest sensitivity to insufficient exposure to sunlight, which is an indirect measure of vitamin D deficiency, in terms of MS risk, both in early childhood and in later adolescent life stages. These results further support that vitamin D is associated with MS risk. There were also seasonal differences in this correlation. In Norway, the correlation was more significant only in the summer, and in a more southerly country like Italy, the correlation was present in both summer and winter. The EnvIMS Study These data come from the EnvIMS Study, a large multinational case-control study of environmental risk factors, including infections, diet, smoking, and sun exposure, associated with MS risk in Norway, Sweden, Canada, Serbia, and Italy. The analysis included 733 cases and 1438 population-based controls from Italy and 959 cases and 1718 population-based controls from Norway. Study participants completed questionnaires that estimated the amount of time spent outdoors during winter months and summer months, with choices ranging from “no outdoor activity” to “most time spent outdoors” for different age groups (under 6 years, 7 to 12 years, 13 to 15 years, 19 to 24 years, and 10 to 15 years). 15, 19 to 24, and 25 to 30). They also answered questions about sunscreen use. The researchers found that the negative correlation between sun exposure and MS became stronger in the Norwegian study group between the ages of 16 and 18 years, after adjusting for gender (OR, 1.79; 95% confidence interval [CI] , 1.28 – 2.52), whereas it was strongest in the Italian group during the period from 0 to 5 years (OR, 1.57; 95% confidence interval, 1.17 – 2.12). These findings suggest that age changes may be associated with MS risk latitude due to vitamin D insufficiency. Sicily, where most of the Italian study participants resided, is located north of 41 degrees north latitude, while the Norwegian latitude varied, being north of 71 degrees north latitude. The study also found a negative correlation between MS risk and sunlight exposure sought in a significant negative correlation (OR, 1.45; 95% confidence interval, 1.05 – 2.00) during the Italian winter, but this was not the case in Norway. In addition, in Norway, sunscreen use in early childhood (before age 6 years) was associated with an increased risk of MS after adjusting for the same period of sun exposure (OR, 1.59; 95% confidence interval, 1.23 – 2.04). Session co-chair George Ebers, PhD, Professor, Department of Clinical Neuroscience, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, UK, commented that the current widespread policy support for sunscreen use is “misguided,” and that while such behavior may affect skin cancer risk, it can also have ” harmful biological effects. Dr. Ebers also noted that vitamin D induces epigenetic changes, and maternal sun exposure may help explain the effect of sun exposure on MS risk in Italy and Norway. “If sun exposure has an effect on offspring, parental sun exposure may also have a role,” he said. BMI and MS risk Another analysis using EnvIMS data found that being overweight, especially in younger Norwegians, was a risk factor for developing MS, but weight did not appear to be a risk factor in the Italian population. Lead author, researcher Kristin Wesnes, PhD, a graduate student at the University of Bergen, Norway, said, “Larger body size in early adulthood appears to be a risk factor for MS in both men and women, with the highest risk in men at age 25 years, and although Norwegian women are at lower risk, their risk is still increasing.” The study included 959 cases (286 males, 673 females) in the Norwegian group, 1,718 controls (462 males, 1,256 females) and 732 cases (261 males, 471 females) and 1,439 controls (471 males, 968 females) in the Italian group. The researchers used body mass index (BMI) to verify body size. Dr. Wesnes noted that other studies, including 2 recent ones from Canada and Sweden, have shown that lower vitamin D levels are associated with obesity and that larger body size in young people can increase MS risk.