CASE-CONTROL STUDY ON CHILDHOOD LEUKEMIA IN LOWER SAXONY, GERMANY - BASIC CONSIDERATIONS, METHODOLOGY, AND SUMMARY OF RESULTS

In two municipalities in Lower Saxony statistically valid clusters wer e observed, which attracted great public interest. Committees were set up to initiate a large variety of on-the-spot-investigations. Finally , it was decided to conduct a case control study throughout Lower Saxo ny to explore potential risk factors which might explain the observed clusters. A limited number of already established and currently discus sed hypotheses was chosen for investigation. The study was based on pa tients registrated at the German Children's Cancer Registry (GCCR). Fo r each child with leukemia diseased between 1988 and 1993 two populati on-based controls (local and state controls) and one tumour control we re selected. Data were collected by means of a questionnaire self-admi nistered by the parents and a telephone interview. In addition, measur ements of electromagnetic fields and radon were performed and inspecti ons of the child's birth record were made for the purpose of confirmin g a potential association between parenteral vitamin K prophylaxis and leukemia or tumours. This paper presents the concept and basic consid erations of the study, its design and statistical evaluation. Response rates and a summary of results will be presented, too. The paper will serve as a reference for subsequent publications about more detailed analyses of specific potential risk factors. 425 parents of diseased c hildren and 610 of non-diseased children were asked for participation. The rates of response were 82% for families with diseased and 71% for families with non-diseased children. In total, 781 parents participat ed in the study. The most important results are as follows: The Greave s' hypothesis (9, 10) was supported by the following results: Tn child ren diseased with leukemia, vaccinations were less frequent, virus-rel ated infections occurred more rarely, these children were more frequen tly first-born children and more frequently breast-feed, and they poss ibly had fewer contacts with other children in infancy. Our data do no t show a significant association between parenteral vitamin K prophyla xis and leukemia or tumours (17).