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

A 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.There 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.This 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.Leukaemias are the most common cancers in childhood. Known causal factors for childhood leukaemias include genetic and familial factors, ionizing radiation, and cancer chemotherapy drugs, but together they account for a tiny proportion of cases. Two major hypotheses from Kinlen [1] and Greaves [2] have suggested that infections may be involved in the aetiology of childhood leukaemias. Feline leukaemia virus is well recognised as a cause of leukaemia in cats [3].Infections in childhood may relate to demographic factors such as pa