Birth characteristics and the risk of childhood leukaemias and lymphomas in New Zealand: a case-control study

Abstract

BackgroundSome studies have found that lower parity and higher or lower social class (depending on the study) are associated with increased risks of childhood acute lymphoblastic leukaemia (ALL). Such findings have led to suggestions that infection could play a role in the causation of this disease. An earlier New Zealand study found a protective effect of parental marriage on the risk of childhood ALL, and studies elsewhere have reported increased risks in relation to older parental ages. This study aimed to assess whether lower parity, lower social class, unmarried status and older parental ages increase the risk of childhood ALL (primarily). These variables were also assessed in relation to the risks of childhood acute non-lymphoblastic leukaemia, non-Hodgkin's lymphomas and Hodgkin's disease.MethodsA case control study was conducted. The cases were 585 children diagnosed with leukaemias or lymphomas throughout New Zealand over a 12 year period. The 585 age and sex matched controls were selected at random from birth records. Birth records from cases (via cancer registration record linkage) and from controls provided accurate data on maternal parity, social class derived from paternal occupation, maternal marital status, ages of both parents, and urban status based on the address on the birth certificate. Analysis was by conditional logistic regression.ResultsThere were no statistically significant associations overall between childhood ALL and parity of the mother, social class, unmarried maternal status, increasing parental ages (continuous analysis), or urban status. We also found no statistically significant associations between the risks of childhood acute non-lymphoblastic leukaemia, non-Hodgkin lymphomas, or Hodgkin's disease and the variables studied.ConclusionThis study showed no positive results though of reasonable size, and its record linkage design minimised bias. Descriptive studies (eg of time trends of ALL) show that environmental factors must be important for some diagnoses. Work has been done on the risk of ALL in relation to chemicals (eg pesticides) and drugs, dietary factors (eg vitamins), electromagnetic fields and infectious hypotheses (to name some); but whether these or other unknown factors are truly important remains to be seen.

Childhood hodgkin's lymphoma, non‐hodgkin's lymphoma and factors related to the immune system: The escale study (SFCE)

“…Birth order may be of importance for the age at exposure to common infections, assuming that children of later birth order are more likely to be exposed to infectious agents at an earlier age via older siblings. Most studies reported odds ratios lower than one for the highest birth order, but rarely significantly, for HL36, 39–41 and NHL 33, 37, 41. In contrast, two studies found an increased risk of HL with increasing birth order 26, 38.…”

“…More studies have investigated birth order 26, 33, 34, 36–41. Birth order may be of importance for the age at exposure to common infections, assuming that children of later birth order are more likely to be exposed to infectious agents at an earlier age via older siblings.…”

Epidemiology of childhood acute myeloid leukemia

“…Only one study found a significant relationship between paternal age and childhood AML, but this finding was only significant when not adjusted for maternal age 24. Other studies found non‐significant positive associations with older paternal age 28, 30, 32, 33, 36, a non‐significant inverse associations with older paternal age 37–39, or an unspecified non‐significant difference 41. For studies with over 200 cases, results were mixed as well.…”

“…One found a significant linear trend for increasing birth order in infants (P ¼ 0.04) [44], another reported a significant association for three or more previous live births compared to one or two (OR ¼ 1.9; 95% CI 1.0, 3.3) [33], and the third found an association for three or more previous live births compared to none (OR ¼ 1.6; 95% CI 1.0, 2.8) [34]. Studies with non-significant associations have suggested an increased risk with increasing birth order or prior live births [25,28,[38][39][40]46], but others found inconsistent results or possible negative associations [27,29,30,36,37,41,47,48].…”

Reproductive history, infertility treatment, and the risk of acute leukemia in children with down syndrome

“…Previous studies in children without DS have indicated no or little elevation in risk for advanced maternal age, [10][11][12][13][14][15][16][17][18][19] prior fetal loss, 12,[14][15][16][17][20][21][22][23][24][25] prior contraceptive use, 15,[26][27][28] time between births, 16,22 and birth order. 12,[14][15][16]20,21,[29][30][31] However, those factors may have a greater impact on the development of leukemia in children with DS, because trisomy 21 may represent a first genetic ''hit,'' and stronger associations may be expected than those reported in studies of children without DS.…”