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Exposure to infant siblings during early life and risk of multiple sclerosis


Ponsonby, AL and Van der Mei, IAF and Dwyer, T and Blizzard, CL and Taylor, BVM and Kemp, A and Simmons, R and Kilpatrick, T, Exposure to infant siblings during early life and risk of multiple sclerosis, Journal of the American Medical Association, 293, (4) pp. 463-469. ISSN 0098-7484 (2005) [Refereed Article]

DOI: doi:10.1001/jama.293.4.463


Context: The "hygiene hypothesis" has implicated sibship as a marker of infection load during early life and suggests that exposure or reexposure to infections can influence the developing immune system. Viral infection has also been implicated in the pathogenesis of multiple sclerosis (MS). Objectives: To evaluate whether exposure to infant siblings in early life is associated with the risk of MS, and to explore the possible mechanism for any apparent protective effect, including altered Epstein-Barr virus (EBV) infection patterns. Design, Setting, and Patients: Population-based case-control study in Tasmania, Australia, from 1999 to 2001 based on 136 cases of magnetic resonance imaging-confirmed MS and 272 community controls, matched on sex and year of birth. Main Outcome Measure: Risk of MS by duration of contact with younger siblings aged less than 2 years in the first 6 years of life. Results: Increasing duration of contact with a younger sibling aged less than 2 years in the first 6 years of life was associated with reduced MS risk (adjusted odds ratios [AORs]: <1 infant-year, 1.00 [reference]; 1 to <3 infant-years, 0.57 [95% confidence interval {CI}, 0.33-0.98]; 3 to <5 infant-years, 0.40 [95% CI, 0.19-0.92]; ≥5 infant-years, 0.12 [95% CI, 0.02-0.88]; test for trend, P=.002). A history of exposure to infant siblings was associated with a reduced IgG response to EBV among controls. Controls with at least 1 infant-year contact had a reduced risk of infectious mononucleosis and a reduced risk of very high composite EBV IgG titers (AOR, 0.33; 95% CI, 0.11-0.98) compared with other controls. The inverse association between higher infant contact and MS was independent of EBV IgG titer. Conclusion: Higher infant sibling exposure in the first 6 years of life was associated with a reduced risk of MS, possibly by altering childhood infection patterns and related immune responses.

Item Details

Item Type:Refereed Article
Research Division:Health Sciences
Research Group:Epidemiology
Research Field:Epidemiology not elsewhere classified
Objective Division:Health
Objective Group:Public health (excl. specific population health)
Objective Field:Preventive medicine
UTAS Author:Ponsonby, AL (Professor Anne Ponsonby)
UTAS Author:Van der Mei, IAF (Professor Ingrid van der Mei)
UTAS Author:Dwyer, T (Professor Terry Dwyer)
UTAS Author:Blizzard, CL (Professor Leigh Blizzard)
UTAS Author:Taylor, BVM (Professor Bruce Taylor)
ID Code:35473
Year Published:2005
Web of Science® Times Cited:118
Deposited By:Menzies Centre
Deposited On:2005-08-01
Last Modified:2010-05-05

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