Leukemia is the most common type of cancer among children and adolescents worldwide. The aim of this umbrella review was (1) to provide a synthesis of the environmental risk factors for the onset of childhood acute lymphoblastic leukemia (ALL) by exposure window, (2) evaluate their strength of evidence and magnitude of risk, and as an example (3) estimate the prevalence in the German population, which determines the relevance at the population level. Relevant systematic reviews and pooled analyses were identified and retrieved through PubMed, Web of Science databases and lists of references. Only two risk factors (low doses of ionizing radiation in early childhood and general pesticide exposure during maternal preconception/pregnancy) were convincingly associated with childhood ALL. Other risk factors including extremely low frequency electromagnetic field (ELF-MF), living in proximity to nuclear facilities, petroleum, benzene, solvent, and domestic paint exposure during early childhood, all showed some level of evidence of association. Maternal consumption of coffee (high consumption/>2 cups/day) and cola (high consumption) during pregnancy, paternal smoking during the pregnancy of the index child, maternal intake of fertility treatment, high birth weight (≥4000 g) and caesarean delivery were also found to have some level of evidence of association. Maternal folic acid and vitamins intake, breastfeeding (≥6 months) and day-care attendance, were inversely associated with childhood ALL with some evidence. The results of this umbrella review should be interpreted with caution; as the evidence stems almost exclusively from case-control studies, where selection and recall bias are potential concerns, and whether the empirically observed association reflect causal relationships remains an open question. Hence, improved exposure assessment methods including accurate and reliable measurement, probing questions and better interview techniques are required to establish causative risk factors of childhood leukemia, which is needed for the ultimate goal of primary prevention.
IntroductionThere have been many meta-analyses of randomised controlled trials on the influence of different diets on obesity-related anthropometric characteristics in adults. However, whether diet interventions can effectively decrease obesity-related anthropometric characteristics remains unclear. The objective of this study is to summarise and synthesise the evidence on the effects of diet on obesity-related anthropometric characteristics in adults by an umbrella review of meta-analyses of randomised controlled trials.Methods and analysisWe will first retrieve English articles only published before 15 December 2021 by searching PubMed, Embase and Web of Science. Only articles that are meta-analyses of randomised controlled trials will be included. Three researchers will independently screen the titles and abstracts of retrieved articles and check the data extracted from each eligible meta-analysis. In each meta-analysis, we will consider calculating the effect size of the mean difference of the effect of each diet on obesity-related anthropometric characteristics in adults using a random-effect model or a fixed-effect model according to heterogeneity. Study heterogeneity (Cochrane’s Q and I2 statistics) and small-study effects (Egger’s test or Begg’s test) will be considered. Evidence of each effect size will be graded according to the NutriGrade scoring system. We will use AMSTAR-2 (A Measurement Tool to Assess Systematic Reviews V.2) to assess the methodological quality of each meta-analysis.Ethics and disseminationThis umbrella review will provide information on the effects of different diets on obesity-related anthropometric characteristics in adults. Ethical approval is not necessary for this study. We will publish the completed umbrella review and related data online.PROSPERO registration numberCRD42021232826.