25 hydroxyvitamin D Epstein Barr virus infection MS environmental risk factors Review adiponectin air pollutant body mass breast feeding child care demyelinating disease disease burden disease course domestic chemical early intervention environmental exposure fatty acid binding protein 4 gamma interferon human interleukin 2 interleukin 6 intestine flora leptin lifestyle modification multiple sclerosis nonhuman nuclear magnetic resonance imaging obesity passive smoking pathogenesis pediatric multiple sclerosis (MS)