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Offspring number, pregnancy, and risk of a first clinical demyelinating event: The AusImmune Study
Methods: Cases (n = 282) were aged 18–59 years with a first clinical diagnosis of CNS demyelination (first clinical demyelinating event [FCD]) and resident within 1 of 4 Australian centers (from latitudes 27° south to 43° south) from 2003 to 2006. Controls (n = 542) were matched to cases on age, sex, and study region, without first clinical diagnosis of CNS demyelination.
Results: Higher offspring number was associated with FCD risk among women (p < 0.001) but not men (p = 0.71); difference in effect; p = 0.001. Among women, higher parity was associated with reduced risk of FCD (adjusted odds ratio 0.51 [95% confidence interval 0.36, 0.72] per birth) with a similar magnitude of effect observed among classic first demyelinating events (adjusted odds ratio 0.47 [95% confidence interval 0.29, 0.74]). The apparent beneficial effect of higher parity was also evident among parous women only (p < 0.001). Among cases, a clear female excess was evident for those with low but not high (4 or more) offspring number. Factors such as human leukocyte antigen DR15 genotype did not appear to modify the association between higher parity and a reduced FCD risk among women.
Conclusions: These findings are consistent with a cumulative beneficial effect of pregnancy. Temporal changes toward an older maternal age of parturition and reduced offspring number may partly underlie the increasing female excess among MS cases over time.
Funding
National Multiple Sclerosis Society
History
Publication title
NeurologyVolume
78Issue
12Pagination
867-874ISSN
0028-3878Department/School
Menzies Institute for Medical ResearchPublisher
Lippincott Williams & WilkinsPlace of publication
530 Walnut St, Philadelphia, USA, Pa, 19106-3621Rights statement
Copyright 2012 AAN Enterprises, Inc.Repository Status
- Restricted