Siblings and the risk of XXXX .

@entity1 @entity31 @entity30 @entity29
BACKGROUND: Environmental exposures in early life have been implicated in the aetiology of @entity29 ( @entity29 ). Siblings are used as proxy markers to characterize patterns of exposure relevant to the risk of @entity29 . METHODS: Some 15,823 @entity1 with @entity31 and 12,668 with @entity30 from the Swedish In- @entity1 Register were compared with 79,546 and 63,035 controls, respectively, in a case-control study. Multiple logistic regression was used to investigate associations with older and younger siblings, and adjustment was made for sex, year of birth, mother's age, region and, additionally, father's social class. RESULTS: Older siblings are associated with a graded increased risk for @entity31 (P for trend <0.001) and an adjusted odds ratio of 1.15 (95% CI 1.07-1.24) for three or more older siblings. Younger siblings are associated with a graded decreased risk for @entity30 (P for trend <0.001) with an adjusted odds ratio of 0.83 (0.76-0.90) for three or more younger siblings. The greatest protective association with @entity30 was seen for younger siblings born within 2 years of the subject. Older maternal age is independently associated with a decreased risk of @entity30 , with P for trend <0.001. Additional adjustment for social class did not substantially alter the results. CONCLUSIONS: Having siblings is associated with the risk and phenotype of developing @entity29 , possibly through their influence on patterns of antigenic exposure in early life. The association of maternal age with @entity30 may reflect age-related changes in maternal immune profile.
