title: Risk factors associated with the onset of relapsing-remitting and primary progressive multiple sclerosis: a systematic review.
abstract: Multiple sclerosis (MS) is a chronic central nervous system disease with a highly heterogeneous course. The aetiology of MS is not well understood but is likely a combination of both genetic and environmental factors. Approximately 85% of patients present with relapsing-remitting MS (RRMS), while 10-15% present with primary progressive MS (PPMS). PPMS is associated with an older onset age, a different sex ratio, and a considerably more rapid disease progression relative to RRMS. We systematically reviewed the literature to identify modifiable risk factors that may be associated with these different clinical courses. We performed a search of six databases and integrated twenty observational studies into a descriptive review. Exposure to Epstein-Barr virus (EBV) appeared to increase the risk of RRMS, but its association with PPMS was less clear. Other infections, such as human herpesvirus-6 and chlamydia pneumoniae, were not consistently associated with a specific disease course nor was cigarette smoking. Despite the vast literature examining risk factors for the development of MS, relatively few studies reported findings by disease course. This review exposes a gap in our understanding of the risk factors associated with the onset of PPMS, our current knowledge being predominated by relapsing-onset MS.
authors: Faculty of Medicine (Neurology), Vancouver Coastal Health Research Institute, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
authors: Kyla A
authors: KA
authors: McKay
authors: Faculty of Medicine (Neurology), Vancouver Coastal Health Research Institute, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
authors: Vivian
authors: V
authors: Kwan
authors: Faculty of Medicine (Neurology), Vancouver Coastal Health Research Institute, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
authors: Thomas
authors: T
authors: Duggan
authors: Faculty of Medicine (Neurology), Vancouver Coastal Health Research Institute, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
authors: Helen
authors: H
authors: Tremlett
mesh_terms: D000900:Anti-Bacterial Agents / Q000009:adverse effects; D002689:Chlamydia / Q000502:physiology; D003276:Contraceptives, Oral / Q000009:adverse effects; D005260:Female; D006801:Humans; D020528:Multiple Sclerosis, Chronic Progressive / Q000453:epidemiology* / Q000821:virology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000453:epidemiology* / Q000821:virology; D036801:Parturition; D011247:Pregnancy; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D014780:Viruses
chemical_list: D000900:Anti-Bacterial Agents; D003276:Contraceptives, Oral