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Published on: December 9, 2015
Risk factors associated with the onset of relapsing-remitting and primary progressive multiple sclerosis: a
Kyla A McKay1, Vivian Kwan1, Thomas Duggan1
1Faculty of Medicine (Neurology), Vancouver Coastal Health Research Institute, Brain Research Centre, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
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.
Insights
This review explores modifiable risk factors for multiple sclerosis (MS) clinical courses. Epstein-Barr virus (EBV) may increase relapsing-MS risk, but primary progressive MS (PPMS) risk factors remain unclear.
Area of Science:
- Neuroimmunology
- Epidemiology of Central Nervous System Diseases
Background:
- Multiple sclerosis (MS) is a chronic, heterogeneous central nervous system disease with unknown etiology, likely involving genetic and environmental factors.
- Relapsing-remitting MS (RRMS) affects 85% of patients, while primary progressive MS (PPMS) affects 10-15%, characterized by older onset, different sex ratio, and faster progression.
Purpose of the Study:
- To systematically review the literature and identify modifiable risk factors associated with different MS clinical courses, specifically RRMS and PPMS.
- To highlight the gap in understanding risk factors for PPMS onset compared to relapsing-onset MS.
Main Methods:
- Systematic literature review across six databases.
- Inclusion and descriptive analysis of twenty observational studies.
- Focus on identifying modifiable risk factors linked to specific MS disease courses.
Main Results:
- Epstein-Barr virus (EBV) exposure was associated with an increased risk of RRMS.
- The association between EBV and PPMS risk was less clear.
- Other infections (HHV-6, Chlamydia pneumoniae) and smoking were not consistently linked to a specific MS disease course.
Conclusions:
- Current research on MS risk factors is predominantly focused on relapsing-onset MS.
- There is a significant knowledge gap regarding modifiable risk factors specifically associated with the onset of primary progressive MS (PPMS).
