Birth order and risk of non-hodgkin lymphoma - True association or bias?

Andrew E. Grulich, Claire M. Vajdic, Michael O. Falster, Eleanor Kane, Karin Ekstrom Smedby, Paige M. Bracci, Silvia De Sanjose, Nikolaus Becker, Jenny Turner, Otoniel Martinez-Maza, Mads Melbye, Eric A. Engels, Paolo Vineis, Adele Seniori Costantini, Elizabeth A. Holly, John J. Spinelli, Carlo La Vecchia, Tongzhang Zheng, Brian C.H. Chiu, Silvia FranceschiPierluigi Cocco, Marc Maynadié, Lenka Foretova, Anthony Staines, Paul Brennan, Scott Davis, Richard K. Severson, James R. Cerhan, Elizabeth C. Breen, Brenda Birmann, Wendy Cozen

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)621-630
Number of pages10
JournalAmerican journal of epidemiology
Issue number6
StatePublished - Sep 15 2010


  • birth order
  • case-control studies
  • lymphoma, non-Hodgkin
  • selection bias
  • social class

ASJC Scopus subject areas

  • Epidemiology


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