Risk Factors Associated with the Onset of Relapsing-Remitting and Primary Progressive Multiple Sclerosis: A Systematic Review

Abstract EN

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.