title: Birth order and risk of non-hodgkin lymphoma--true association or bias?
abstract: There is inconsistent evidence that increasing birth order may be associated with risk of non-Hodgkin lymphoma (NHL). The authors examined the association between birth order and related variables and NHL risk in a pooled analysis (1983-2005) of 13,535 cases and 16,427 controls from 18 case-control studies within the International Lymphoma Epidemiology Consortium (InterLymph). Overall, the authors found no significant association between increasing birth order and risk of NHL (P-trend = 0.082) and significant heterogeneity. However, a significant association was present for a number of B- and T-cell NHL subtypes. There was considerable variation in the study-specific risks which was partly explained by study design and participant characteristics. In particular, a significant positive association was present in population-based studies, which had lower response rates in cases and controls, but not in hospital-based studies. A significant positive association was present in higher-socioeconomic-status (SES) participants only. Results were very similar for the related variable of sibship size. The known correlation of high birth order with low SES suggests that selection bias related to SES may be responsible for the association between birth order and NHL.
authors: HIV Epidemiology and Prevention Program, National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, New South Wales 2052, Australia. agrulich@nchecr.unsw.edu.au
authors: Andrew E
authors: AE
authors: Grulich
authors: Claire M
authors: CM
authors: Vajdic
authors: Michael O
authors: MO
authors: Falster
authors: Eleanor
authors: E
authors: Kane
authors: Karin Ekstrom
authors: KE
authors: Smedby
authors: Paige M
authors: PM
authors: Bracci
authors: Silvia
authors: S
authors: de Sanjose
authors: Nikolaus
authors: N
authors: Becker
authors: Jenny
authors: J
authors: Turner
authors: Otoniel
authors: O
authors: Martinez-Maza
authors: Mads
authors: M
authors: Melbye
authors: Eric A
authors: EA
authors: Engels
authors: Paolo
authors: P
authors: Vineis
authors: Adele Seniori
authors: AS
authors: Costantini
authors: Elizabeth A
authors: EA
authors: Holly
authors: John J
authors: JJ
authors: Spinelli
authors: Carlo
authors: C
authors: La Vecchia
authors: Tongzhang
authors: T
authors: Zheng
authors: Brian C H
authors: BC
authors: Chiu
authors: Silvia
authors: S
authors: Franceschi
authors: Pierluigi
authors: P
authors: Cocco
authors: Marc
authors: M
authors: Maynadié
authors: Lenka
authors: L
authors: Foretova
authors: Anthony
authors: A
authors: Staines
authors: Paul
authors: P
authors: Brennan
authors: Scott
authors: S
authors: Davis
authors: Richard K
authors: RK
authors: Severson
authors: James R
authors: JR
authors: Cerhan
authors: Elizabeth C
authors: EC
authors: Breen
authors: Brenda
authors: B
authors: Birmann
authors: Wendy
authors: W
authors: Cozen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001722:Birth Order; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000145:classification / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D035781:Siblings; D012959:Socioeconomic Factors; D055815:Young Adult