American Journal of Epidemiology Advance Access originally published online on May 4, 2006
American Journal of Epidemiology 2006 163(12):1112-1117; doi:10.1093/aje/kwj148
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Original Contribution |
Sibship Characteristics and Risk of Multiple Sclerosis: A Nationwide Cohort Study in Denmark
1 Department of Epidemiology Research, Danish Epidemiology Science Centre, Statens Serum Institut, Copenhagen, Denmark
2 Department of Neurology, Aarhus University Hospital in Aalborg, Aalborg, Denmark
3 National Institute of Public Health, Copenhagen, Denmark
Correspondence to Dr. Peter Bager, Department of Epidemiology Research, Statens Serum Institute, Artillerivej 5, DK-2300 Copenhagen, Denmark (e-mail: pbg{at}ssi.dk).
It has been hypothesized that age at infection with a common microbial agent may be associated with the risk of multiple sclerosis (MS). The authors addressed this hypothesis by using number of older siblings and other sibship characteristics as an approximation of age at exposure to common infections. Data on family characteristics and vital status from the Danish Civil Registration System were used to establish a cohort of all Danes whose mothers had been born in Denmark since 1935. Persons diagnosed with MS during the period 19681998 were identified through linkage with the Danish Multiple Sclerosis Register. The cohort of 1.9 million Danes was followed for 28.1 million person-years; during that time, 1,036 persons developed MS. Overall, there was no association between number of older siblings, number of younger siblings, total number of siblings, age distance from the nearest younger sibling, or exposure to younger siblings under 2 years of age and risk of MS later in life. There was no association of MS risk with multiple birth (vs. singleton birth) or with the age of the mother or father at birth. These results do not lend support to the hypothesis that number of older siblings or any of the other sibship characteristics studied is associated with risk of MS.
birth order; infection; maternal age; multiple sclerosis; paternal age; risk factors; siblings; twins
Abbreviations: CI, confidence interval; MS, multiple sclerosis; RR, rate ratio