title: Younger siblings, C-reactive protein, and risk of age-related macular degeneration.
abstract: In this study, we examined the relationship between exposure to siblings and 1) the risk of age-related macular degeneration (AMD) and 2) C-reactive protein levels. We retrospectively analyzed pooled cross-sectional data from 2 studies: the Cardiovascular Health and Age-Related Maculopathy Study (2001-2002) and the Age-Related Maculopathy Statin Study (2004-2006). Associations between number of siblings and AMD were assessed by using multinomial logistic regression. Associations between number of siblings and C-reactive protein levels were examined by using a generalized linear model for γ distribution. A higher number of younger siblings was associated with significantly lower odds of early AMD in those with a family history of AMD (odds ratio = 0.2, 95% confidence interval: 0.1, 0.8) (P = 0.022) but was unrelated to AMD for those who had no family history of the disease (odds ratio = 1.0, 95% confidence interval: 0.9, 1.2) (P = 0.874). A higher number of younger siblings correlated with lower C-reactive protein levels (β = -0.19, 95% confidence interval: -0.38, -0.01) (P = 0.036). This supports the theory that immune modulation contributes to AMD pathogenesis and suggests that exposure to younger siblings might be protective when there is a family history of AMD.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Cohn
authors.forename: Lucy
authors.initials: L
authors.lastname: Busija
authors.forename: Liubov D
authors.initials: LD
authors.lastname: Robman
authors.forename: Peter N
authors.initials: PN
authors.lastname: Dimitrov
authors.forename: Mary
authors.initials: M
authors.lastname: Varsamidis
authors.forename: Lyndell L
authors.initials: LL
authors.lastname: Lim
authors.forename: Paul N
authors.initials: PN
authors.lastname: Baird
authors.forename: Robyn H
authors.initials: RH
authors.lastname: Guymer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001722:Birth Order; D002097:C-Reactive Protein / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D017242:Complement Factor H / Q000235:genetics / Q000276:immunology; D003430:Cross-Sectional Studies; D016207:Cytokines / Q000032:analysis; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood; D016014:Linear Models; D016015:Logistic Models; D008268:Macular Degeneration / Q000209:etiology* / Q000235:genetics / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D035781:Siblings; D014739:Victoria
chemical_list: D015415:Biomarkers; C493495:CFH protein, human; D016207:Cytokines; D017242:Complement Factor H; D002097:C-Reactive Protein
keywords: C-reactive protein; age-related macular degeneration; inflammation; sibling exposure