Table 1:

Environmental Factors for MS Risk and Disease Course

Environmental Factor	Risk for POMS	Impact on MS Disease Course
Geography	Higher latitude correlates to a higher risk of POMS, greatest impact when < 15 years old [1]	No current evidence
Vitamin Deficiencies	Low levels of vitamin D are associated with a higher risk for POMS [16,17] More sunlight exposure is associated with reduced risk for POMS [19,20]	Higher vitamin D level is associated with a decreased risk for relapse, decreased risk of new T2 lesions, and decreased risk of disability [10,94]
Diet and Gut Microbiome	Gut microbiota varies in POMS compared to healthy controls [25–28]	Increased fat intake is associated with a higher risk for relapse [100] Increased vegetable intake is associated with lower risk for relapse [100] Certain microbiota are associated with an increased relapse risk [101]
Metabolic Syndrome and Obesity	Metabolic syndrome is more frequent in adult MS versus controls [37–39] Obesity is associated with an increased risk of POMS [41]	Obesity correlates with higher rates of depression and fatigue Obesity is linked with greater degrees of normalized gray matter and brain parenchymal volume loss [110]
Smoking Exposure	Smoking and secondhand exposure are associated with an increased risk of POMS [56]	Smokers develop greater degrees of brain atrophy, higher T2 lesion volume, and hastened progression of disability [29]
Air Pollution	Higher ozone concentrations are associated with a higher risk for MS [62]	Higher PM10 levels are associated with greater inflammatory activity on MRI and higher disability [29]
Infection	A remote history of EBV infection is associated with an increased MS risk [70]	Trials are currently underway assessing EBV vaccines, antivirals, and immunotherapy
Perinatal Factors	Breastfeeding may reduce the risk of MS in children [77]	No current evidence

Abbreviations: EBV = Epstein Barr virus; EDSS = Expanded Disability Status Scale; MRI = magnetic resonance imaging; MS = multiple sclerosis; POMS = pediatric-onset multiple sclerosis