Environmental risk factors for multiple sclerosis. Part II: Noninfectious factors

Abstract

As discussed in Part I of this review, the geographic distribution of multiple sclerosis (MS) and the change in risk among migrants provide compelling evidence for the existence of strong environmental determinants of MS, where "environmental" is broadly defined to include differences in diet and other behaviors. As we did for infections, we focus here primarily on those factors that may contribute to explain the geographic variations in MS prevalence and the change in risk among migrants. Among these, sunlight exposure emerges as being the most likely candidate. Because the effects of sun exposure may be mediated by vitamin D, we also examine the evidence linking vitamin D intake or status to MS risk. Furthermore, we review the evidence on cigarette smoking, which cannot explain the geographic variations in MS risk, but may contribute to the recently reported increases in the female/male ratio in MS incidence. Other proposed risk factors for MS are mentioned only briefly; although we recognize that some of these might be genuine, evidence is usually sparse and unpersuasive.

Vitamin D supplementation differentially affects seasonal multiple sclerosis disease activity

“…The generally recognized MS risk factor hypovitaminosis D (Ascherio & Munger, 2007;Hanwell & Banwell, 2011) is defined as a 25-hydroxyvitamin D (25(OH)D) concentration below 50 nmol/L and is prevalent in approximately 57% of German adults (Hintzpeter, Mensink, Thierfelder, Müller, & Scheidt-Nave, 2008). Experimental data show that vitamin D (VD) possesses anti-inflammatory and immunomodulatory properties through inhibition of dendritic cell differentiation, induction of T regulatory cells, blockage of Th17 differentiation, and down-regulation of Th1 immune responses (Farias et al, 2013;Hamzaoui et al, 2014;Lemire, Archer, Beck, & Spiegelberg, 1995).…”

Neuropilin-1 attenuates autoreactivity in experimental autoimmune encephalomyelitis

“…MS patients develop paralysis because of immune-mediated axonal damage. MS is generally considered to be an autoimmune disease orchestrated by T H -1 and T H -17 lymphocytes, although various genetic and environmental factors also play a part in disease etiology (2,3). Evidence for the role of immune cells in MS pathogenesis is provided by studies using the mouse model experimental autoimmune encephalomyelitis (EAE).…”

Multiple Sclerosis in West Africa, about a Case Confirmed at Ouagadougou, Burkina Faso

“…Evolution was in favor of remitting form second relapse, after a first episode in 2011. Multiple Sclerosis (MS) is a multifactorial disease, resulting from an interaction between genetics and unknown environmental factors [12][13][14][15]. In this case, no environmental or genetic factor permits suspecting MS, as viral infections (EBV...), hygiene ("excessive" hygiene appears to increase the risk), parasites (that protect), tobacco (which increases risk and aggravates pre-existing disease).…”