title: Perinatal and family risk factors for non-Hodgkin lymphoma in early life: a Swedish national cohort study.
abstract: BACKGROUND
  The incidence of non-Hodgkin lymphoma (NHL) in early life has increased in recent decades, but the relevant risk factors remain largely unknown. We examined perinatal and family risk factors for NHL in childhood through young adulthood.
  
  
  METHODS
  We conducted a national cohort study of 3 571 574 individuals born in Sweden in 1973-2008 who were followed for incidence of NHL through 2009 (ages 0-37 years). Detailed information on perinatal and family characteristics and NHL diagnoses were obtained from national birth and cancer registries. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between perinatal and family variables and NHL; P values are from two-sided tests.
  
  
  RESULTS
  There were 936 NHL case patients identified in 66.3 million person-years of follow-up. Independent risk factors for NHL included family history of NHL in either a sibling (adjusted HR = 9.84; 95% CI = 2.46 to 39.41; P = .001) or parent (adjusted HR = 2.36; 95% CI = 1.27 to 4.38; P = .007); high fetal growth (for ≥ 2 SDs relative to 0 to <1 SD from the mean: adjusted HR = 1.64; 95% CI = 1.19 to 2.25; P = .002); older maternal age (adjusted HR for each 5-year increment = 1.11; 95% CI = 1.04 to 1.19; P (trend) = .004); low birth order (adjusted HR for each increment of one birth = 0.91; 95% CI = 0.84 to 0.99; P (trend) = .02); and male sex (adjusted HR = 1.58; 95% CI = 1.38 to 1.80; P < .001). Male sex was associated with onset of NHL before 15 years of age but not with later-onset NHL, whereas the other risk factors did not vary by age at diagnosis. No association was found between gestational age at birth, twinning, paternal age, or parental education and NHL.
  
  
  CONCLUSIONS
  In this large national cohort study, family history of NHL, high fetal growth, older maternal age, low birth order, and male sex were independent risk factors for NHL in early life.
authors.affiliation: Department of Medicine, Stanford University, 900 Blake Wilbur Dr, Stanford, CA 94304-2205,USA. kccrump@stanford.edu
authors.forename: Casey
authors.initials: C
authors.lastname: Crump
authors.forename: Kristina
authors.initials: K
authors.lastname: Sundquist
authors.forename: Weiva
authors.initials: W
authors.lastname: Sieh
authors.forename: Marilyn A
authors.initials: MA
authors.lastname: Winkleby
authors.forename: Jan
authors.initials: J
authors.lastname: Sundquist
mesh_terms: D000293:Adolescent; D000328:Adult; D001722:Birth Order; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005190:Family; D005260:Female; D047109:Fetal Development; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008228:Lymphoma, Non-Hodgkin / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D008423:Maternal Age; D008487:Medical History Taking; D016017:Odds Ratio; D018743:Perinatal Care; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D017678:Sex Distribution; D012737:Sex Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult