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

Childhood acute lymphoblastic leukemia and indicators of early immune stimulation: a Childhood Leukemia International Consortium study

The associations between childhood acute lymphoblastic leukemia (ALL) and several proxies of early stimulation of the immune system, that is, day-care center attendance, birth order, maternally reported common infections in infancy, and breastfeeding, were investigated by using data from 11 case-control studies participating in the Childhood Leukemia International Consortium (enrollment period: 1980-2010). The sample included 7,399 ALL cases and 11,181 controls aged 2-14 years. The data were collected by questionnaires administered to the parents. Pooled odds ratios and 95% confidence intervals were estimated by unconditional logistic regression adjusted for age, sex, study, maternal education, and maternal age. Day-care center attendance in the first year of life was associated with a reduced risk of ALL (odds ratio = 0.77, 95% confidence interval: 0.71, 0.84), with a marked inverse trend with earlier age at start (P < 0.0001). An inverse association was also observed with breastfeeding duration of 6 months or more (odds ratio = 0.86, 95% confidence interval: 0.79, 0.94). No significant relationship with a history of common infections in infancy was observed even though the odds ratio was less than 1 for more than 3 infections. The findings of this large pooled analysis reinforce the hypothesis that day-care center attendance in infancy and prolonged breastfeeding are associated with a decreased risk of ALL.

Childhood acute lymphoblastic leukaemia and indicators of early immune stimulation: the Estelle study (SFCE)

Background:

Factors related to early stimulation of the immune system (breastfeeding, proxies for exposure to infectious agents, normal delivery, and exposure to animals in early life) have been suggested to decrease the risk of childhood acute lymphoblastic leukaemia (ALL).

Methods:

The national registry-based case–control study, ESTELLE, was carried out in France in 2010–2011. Population controls were frequency matched with cases on age and gender. The participation rates were 93% for cases and 86% for controls. Data were obtained from structured telephone questionnaires administered to mothers. Odds ratios (OR) were estimated using unconditional regression models adjusted for age, gender, and potential confounders.

Results:

In all, 617 ALL and 1225 controls aged ⩾1 year were included. Inverse associations between ALL and early common infections (OR=0.8, 95% confidence interval (CI): 0.6, 1.0), non-first born (⩾3 vs 1; OR=0.7, 95% CI: 0.5, 1.0), attendance of a day-care centre before age 1 year (OR=0.7, 95% CI: 0.5, 1.0), breastfeeding (OR=0.8, 95% CI: 0.7, 1.0), and regular contact with pets (OR=0.8, 95% CI: 0.7, 1.0) in infancy were observed.

Conclusions:

The results support the hypothesis that conditions promoting the maturation of the immune system in infancy have a protective role with respect to ALL.

Birth characteristics and risk of lymphoma in young children

BACKGROUND

Lymphoma is the third most common childhood malignancy and comprises two types, Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). The etiology of pediatric lymphomas is largely unknown, but has been suggested to have prenatal origins.

METHODS

In this population-based study, California birth certificates were identified for 478 lymphoma cases diagnosed in children 0-5 years of age between 1988 and 2007; 208,015 controls frequency-matched by birth year were randomly selected from California birth records.

RESULTS

Compared to non-Hispanic whites, Hispanic children had an increased risk of HL (odds ratio (OR) and 95% confidence interval (CI) 2.43 [1.14, 5.17]), and in particular, were diagnosed more often with the mixed cellularity subtype. For all types of lymphoma, we observed an about twofold risk increase with indicators for high risk pregnancies including tocolysis, fetopelvic disproportion and previous preterm birth. NHL risk doubled with the complication premature rupture of membranes (OR and 95% CI 2.18 [1.12, 4.25]) and HL with meconium staining of amniotic fluids (OR and 95% CI 2.55 [1.01, 6.43]).

CONCLUSION

These data support previously reported associations between Hispanic ethnicity and HL and suggest that pregnancy related factors, such as intra-uterine infections and factors associated with preterm labor, may be involved in lymphoma pathogenesis.

Epidemiology of childhood acute myeloid leukemia

Although leukemia is the most common childhood cancer diagnosis, the subtype, acute myeloid leukemia (AML), is less common and fewer etiologic studies exist. This review summarizes the major risk factors for AML. We searched the literature using PubMed for articles on childhood AML and reviewed 180 articles. While few risk factors are definitive, we identified several with consistent evidence of a possible effect. Thorough analysis of genetic and epigenetic factors is missing from this literature and methodological issues are unresolved. Future studies should more closely examine causal mechanisms, improve exposure measurement, and include analysis using genetic and epigenetic factors.

Socioeconomic status and other characteristics in childhood leukemia

BACKGROUND

Leukemia is the most prevalent childhood cancer, and Acute Lymphoblastic Leukemia (ALL) constitutes 75% of all cases. Some epidemiological studies have shown a relationship between socioeconomic status (SES) and some childhood cancers. In the present study, an attempt was made to assess socioeconomical status in a case-control study.

MATERIALS AND METHODS

In 2010, a case-control study was conducted on 100 cases of acute lymphoblastic leukemia aged 1 to14 years in Department of Pediatric Oncology of Dr.Sheikh Hospital in Mashhad - Iran and matched age and sex with 400 healthy controls. Data was collected by interview using a questionnaire. Ninety five percent confidence intervals were used to measure the relationship between childhood Acute Lymphoblastic Leukemia and parental education, income status, father's job (Socioeconomic status), number of children, birth score and paternal smoking.

RESULTS

There was a significant difference in parental education level, income status, and number of children, birth score, father's job and paternal smoking between two groups. Regression analysis showed that the risk of childhood ALL associated with paternal smoking, and father's high risk job. Fifty percent cases and thirty five percent of control groups located in upper lower and lower middle class of socioeconomic status, respectively. There is a meaningful different between socioeconomic status in two groups. But the risk of childhood ALL did not associate with socioeconomic status.

CONCLUSION

The results suggest that paternal smoking and father's high risk job are related to risk of childhood leukemia. It should be considered for planning support.

Parental exposure to carcinogens and risk for childhood acute lymphoblastic leukemia, Colombia, 2000-2005

INTRODUCTION

The objective of this study was to determine the risk factors for childhood acute lymphoblastic leukemia (ALL) and, in particular, the role of parental occupational exposure to carcinogenic and probably carcinogenic hydrocarbons before the child's conception.

METHODS

For this case-control study, cases were children younger than 15 years who were newly diagnosed with ALL between January 2000 and March 2005 at 1 of 6 Colombian hospitals. An interview with both parents of 170 children (85 cases and 85 individually matched neighborhood controls) gathered information about each child's exposures and parental demographic and occupational characteristics, medical history, health risk behaviors, and pregnancy and birth history. A job-exposure matrix was used to classify parental exposure to hydrocarbons on the basis of the main industrial activity of each workplace where parents worked before (both parents) or during the index pregnancy (mother only). Conditional odds ratios and 95% confidence intervals were calculated by period of exposure (preconception, pregnancy, and childhood).

RESULTS

The risk of childhood ALL was linked to 1) parental occupational exposure to hydrocarbons before conception, 2) parental smoking before conception, 3) maternal low socioeconomic status during pregnancy, and 4) higher maternal age (≥35 y) at the child's birth.

CONCLUSION

These findings suggest an association between childhood ALL and parental occupational exposure to carcinogenic and probably carcinogenic hydrocarbons before conception. Outcomes depended on the parent exposed. Future research should investigate the additive or multiplicative role of other environmental sources of hydrocarbons.

Childhood Hodgkin's lymphoma, non-Hodgkin's lymphoma and factors related to the immune system: the Escale Study (SFCE)

The study investigated the role of factors considered related to the early stimulation of the immune system in the aetiology of childhood lymphoma. The national registry-based case-control study, Escale, was carried out in France over the period 2003-2004. Population controls were frequency matched with the cases on age and gender. Data were obtained from structured telephone questionnaires administered to mothers. Odds ratios (ORs) were estimated using unconditional regression models adjusted for potential confounders. Data from 128 cases of Hodgkin's lymphoma (HL) aged 5-14 years, 164 cases of non-Hodgkin's lymphoma (NHL) aged 2-14 years and 1,312 controls were analyzed. Negative associations were observed between HL and day care attendance [OR = 0.5 (0.2-1.2)] and between HL and repeated early common infections among non-breastfed children [OR = 0.3 (.2-0.7), p = 0.003] [OR for breastfed children: 1.0 (.5-2.1)], but not for the other factors investigated. Negative associations were observed between NHL and birth order 3 or more [OR = 0.7 (0.4-1.1)], prolonged breastfeeding [OR = 0.5 (0.3-1.0)], regular contact with farm animals [OR = 0.5 (0.3-1.0)], frequent farm visits in early life [OR = 0.6 (0.4-1.1)] and history of asthma [OR = 0.6 (0.3-1.1)]. In conclusion, the results partly support the hypothesis that an abnormal maturation of the immune system may play a role in childhood HL or NHL, and call for further investigations.

Maternal and perinatal factors associated with hospitalised infectious mononucleosis in children, adolescents and young adults: record linkage study

BACKGROUND

There is current interest in the role of perinatal factors in the aetiology of diseases that occur later in life. Infectious mononucleosis (IM) can follow late primary infection with Epstein-Barr virus (EBV), and has been shown to increase the risk of multiple sclerosis and Hodgkin's disease. Little is known about maternal or perinatal factors associated with IM or its sequelae.

METHODS

We investigated perinatal risk factors for hospitalised IM using a prospective record-linkage study in a population in the south of England. The dataset used, the Oxford record linkage study (ORLS), includes abstracts of birth registrations, maternities and in-patient hospital records, including day case care, for all subjects in a defined geographical area. From these sources, we identified cases of hospitalised IM up to the age of 30 years in people for whom the ORLS had a maternity record; and we compared perinatal factors in their pregnancy with those in the pregnancy of children who had no hospital record of IM.

RESULTS

Our data showed a significant association between hospitalised IM and lower social class (p = 0.02), a higher risk of hospitalised IM in children of married rather than single mothers (p < 0.001), and, of marginal statistical significance, an association with singleton birth (p = 0.06). The ratio of observed to expected cases of hospitalised IM in each season was 0.95 in winter, 1.02 in spring, 1.02 in summer and 1.00 in autumn. The chi-square test for seasonality, with a value of 0.8, was not significant.Other factors studied, including low birth weight, short gestational age, maternal smoking, late age at motherhood, did not increase the risk of subsequent hospitalised IM.

CONCLUSIONS

Because of the increasing tendency of women to postpone childbearing, it is useful to know that older age at motherhood is not associated with an increased risk of hospitalised IM in their children. We have no explanation for the finding that children of married women had a higher risk of IM than those of single mothers. Though highly significant, it may nonetheless be a chance finding. We found no evidence that such perinatal factors as birth weight and gestational age, or season of birth, were associated with the risk of hospitalised IM.

Childhood acute leukemia, early common infections, and allergy: The ESCALE Study

This study investigated the role of factors considered related to early stimulation of the immune system in the etiology of childhood acute leukemia. The national registry-based case-control study ESCALE was carried out in France in 2003-2004. Population controls were frequency matched to cases on age and gender. Data were obtained from structured telephone questionnaires administered to mothers. Odds ratios were estimated using unconditional regression models adjusted for potential confounders. Included were 634 acute lymphoblastic leukemia cases, 86 acute myeloblastic leukemia cases, and 1,494 controls aged ≥1 year. Negative associations were observed between acute lymphoblastic leukemia and birth order (P for trend < 0.0001), attendance at a day-care center before age 1 year (odds ratio (OR) = 0.8, 95% confidence interval (CI): 0.6, 1.1), prolonged breastfeeding (OR = 0.7, 95% CI: 0.5, 1.0), repeated early common infections (OR = 0.7, 95% CI: 0.6, 0.9), regular contact with farm animals (OR = 0.6, 95% CI: 0.5, 0.8), frequent farm visits in early life (OR = 0.4, 95% CI: 0.3, 0.6), and history of asthma (OR = 0.7, 95% CI: 0.4, 1.0) or eczema (OR = 0.7, 95% CI: 0.6, 0.9). Results support the hypothesis that repeated early infections and asthma may play a role against childhood acute leukemia.

Family characteristics as risk factors for childhood acute lymphoblastic leukemia: a population-based case-control study

Background

To date, few risk factors for childhood acute lymphoblastic leukemia (ALL) have been confirmed and the scientific literature is full of controversial “evidence.” We examined if family characteristics, particularly maternal and paternal age and number of older siblings, were risk factors for childhood acute lymphoblastic leukemia (ALL).

Methodology/Principal Findings

In this population-based nationwide matched case-control study, patients 0–14 years of age with ALL diagnosed 1991–2006 and registered in the Swiss Childhood Cancer Registry were linked with their census records of 1990 and 2000. Eight controls per case were selected from the census. The association between family characteristics and ALL was analyzed by conditional logistic regressions. We found that increasing maternal age was associated with incidence of ALL in the offspring (OR per 5-year increase in maternal age 1.18, 95% CI 1.05–1.31; p = 0.004), remaining stable (trend OR 1.14, 95% CI 0.99–1.31; p = 0.060) after adjustment for other risk factors. The association with paternal age was weaker (OR per 5-year increase 1.14, 95% CI 1.01–1.28, p = 0.032) and disappeared after adjustments. Number of older siblings was not associated with risk of ALL in the overall group of children aged 0–14 years at diagnosis. However, we found a negative trend between number of older siblings and ALL diagnosed at age 0–4 years (OR per sibling 0.85, 95% CI 0.68–1.06; p = 0.141) and a positive trend for ALL diagnosed at age 5–9 (OR 1.34, 95% CI 1.05–1.72; p = 0.019), with some evidence for an effect modification (p-value for interaction  = 0.040).

Conclusions

As in other studies, increasing maternal, but not paternal age was associated with risk of ALL. We found only a weak association with the number of older siblings, suggesting a delay in disease manifestation rather than a decrease in incidence.

Host, family and community proxies for infections potentially associated with leukaemia

Three hypotheses have proposed the involvement of infections in the aetiology of childhood leukaemia, suggesting either a specific leukaemogenic infection or a series of common infections that lead to a dysregulation of the immune system. Much of the evidence for the link with infections has been based on epidemiological observations, often using proxy measures of infection. Proxy measures include population mixing, parental occupation, age distribution of incidence, spatial and space-time clustering of cases, birth order and day care during infancy. This paper discusses the proxies used and examines to what extent a commonly used proxy measure, birth order, is a fair representation of either specific infections or general infectious load. It is clear that although leukaemia, and other diseases, may be linked with infections, one needs to (1) measure specific and general infections with more accuracy and (2) understand how proxy measures relate to real infections in the population.

Parental and infant characteristics and childhood leukemia in Minnesota

BACKGROUND

Leukemia is the most common childhood cancer. With the exception of Down syndrome, prenatal radiation exposure, and higher birth weight, particularly for acute lymphoid leukemia (ALL), few risk factors have been firmly established. Translocations present in neonatal blood spots and the young age peak of diagnosis suggest that early-life factors are involved in childhood leukemia etiology.

METHODS

We investigated the association between birth characteristics and childhood leukemia through linkage of the Minnesota birth and cancer registries using a case-cohort study design. Cases included 560 children with ALL and 87 with acute myeloid leukemia (AML) diagnoses from 28 days to 14 years. The comparison group was comprised of 8,750 individuals selected through random sampling of the birth cohort from 1976-2004. Cox proportional hazards regression specific for case-cohort studies was used to compute hazard ratios (HR) and 95% confidence intervals (CIs).

RESULTS

Male sex (HR = 1.41, 95% CI 1.16-1.70), white race (HR = 2.32, 95% CI 1.13-4.76), and maternal birth interval > or = 3 years (HR = 1.31, 95% CI 1.01-1.70) increased ALL risk, while maternal age increased AML risk (HR = 1.21/5 year age increase, 95% CI 1.0-1.47). Higher birth weights (>3798 grams) (HRALL = 1.46, 1.08-1.98; HRAML = 1.97, 95% CI 1.07-3.65), and one minute Apgar scores < or = 7 (HRALL = 1.30, 95% CI 1.05-1.61; HRAML = 1.62, 95% CI 1.01-2.60) increased risk for both types of leukemia. Sex was not a significant modifier of the association between ALL and other covariates, with the exception of maternal education.

CONCLUSION

We confirmed known risk factors for ALL: male sex, high birth weight, and white race. We have also provided data that supports an increased risk for AML following higher birth weights, and demonstrated an association with low Apgar scores.