Birth order, atopy, and risk of non-Hodgkin lymphoma.
BACKGROUND
Immune deficiency is a strong risk factor for non-Hodgkin lymphoma (NHL), but whether or not other forms of immune dysregulation are associated with NHL risk is unknown. We investigated associations between atopy, which is associated with a Th2-dominant immune response, and NHL risk. Because late birth order and childhood crowding are inversely associated with atopy, we also investigated their associations with NHL risk.


METHODS
We carried out a population-based case-control study among adults aged 20-74 years in New South Wales and the Australian Capital Territory, Australia. NHL patients without clinically apparent immune deficiency (N = 704) were selected from a cancer registry, and control subjects (N = 694) were randomly selected from state electoral rolls and frequency-matched to case patients by age, sex, and area of residence. Birth order, childhood crowding, and history of atopic conditions (hay fever, asthma, eczema, and specific allergies) were assessed by questionnaire and interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated from logistic regression models that included the matching variables as covariates.


RESULTS
The odds ratios for developing NHL were 0.52 (95% CI = 0.32 to 0.84) for only children, 0.55 (95% CI = 0.40 to 0.75) for first-born children, 0.70 (95% CI = 0.51 to 0.96) for second-born children, and 0.81 (0.57 to 1.14) for third-born children (all compared with fourth- or later-born children) (P(trend)<.001). Indicators of crowding in later childhood, such as sharing a bed or bedroom, were not associated with NHL risk. A history of atopic conditions was associated with a reduced risk of NHL; this reduction was statistically significant for hay fever (OR = 0.65, 95% CI = 0.52 to 0.82) and food allergies (OR = 0.29, 95% CI = 0.20 to 0.42).


CONCLUSIONS
Early birth order and its immunologic consequence, a Th2-dominated immune response, as reflected by a history of atopic disease, are associated with a reduced risk of NHL.
Grulich
Andrew Edwin
AE
National Centre in HIV Epidemiology and Clinical Research, University of NSW, Sydney, Australia. agrulich@nchecr.unsw.edu.au
Vajdic
Claire Melissa
CM
Kaldor
John Martin
JM
Hughes
Ann Maree
AM
Kricker
Anne
A
Fritschi
Lin
L
Turner
Jennifer Jane
JJ
Milliken
Sam
S
Benke
Geza
G
Armstrong
Bruce Konrad
BK
D000328:Adult; D000368:Aged; D001249:Asthma / Q000453:epidemiology / Q000276:immunology; D020958:Australian Capital Territory; D001722:Birth Order; D016022:Case-Control Studies; D004485:Eczema / Q000453:epidemiology / Q000276:immunology; D005260:Female; D005512:Food Hypersensitivity / Q000453:epidemiology / Q000276:immunology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology* / Q000276:immunology*; D008228:Lymphoma, Non-Hodgkin / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D009517:New South Wales; D016017:Odds Ratio; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology / Q000276:immunology; D018570:Risk Assessment; D011795:Surveys and Questionnaires