Assessing the Quality of Case- Control Studies: EMFs and Childhood Leukemia By: Sandy Hayre Dr. William Bailey Meghan Wagner Exponent

Epidemiology Epidemiology- the study of the frequency and distribution of disease and health in human populations, and the factors that contribute to disease and health events There are several types of studies used in epidemiology:  Clinical trial  Prospective cohort  Retrospective cohort  Case-control- compares persons without a disease (controls) to persons with a disease (cases) to see if they differ on any factors or exposures of interest

Quality of Case-control Studies Studies of higher quality should receive more weight when asking the question: “Does this exposure cause this disease?” Factors that affect the validity of a case-control study:  Bias  Chance  Confounding  Study design  Exposure assessment

Objective Objective: To evaluate the quality of case-control studies that deal with exposure to electric and magnetic fields (EMFs) and childhood leukemia We gathered all case-control studies on EMFs and childhood leukemia through an extensive search and assessed them individually

Electric and Magnetic Fields Anything that generates, transmits or uses electricity produces electric and magnetic fields Electric Fields - the result of voltages applied to electrical conductors and equipment Magnetic Fields - produced by the flow of electric currents

Methods: Assessing EMF and Childhood Leukemia Case-Control Studies Factors evaluated in each study:  Case/control source population  Case/control ascertainment  Case/control inclusion criteria  Case/control exclusion criteria  Matching variables  Case/control participation rate  Number of cases/controls used in analysis after exclusions  Exposure assessment

Future Agenda Use collected data to determine which studies should be weighed more heavily than others Determine what the most effective approach is to evaluating case-control studies:  Checklist  Numerical ranking system

References National Health and Medical Research Council, (1999).How to review the evidence: systematic identification and review of the scientific literature. Liddle, J, Williamson, M, & Irwig, L (December 1996). Method for evaluating research guideline evidence. NSW Health. Task Force on Community Preventive Services, (2000).Data collection instrument and procedure for systematic reviews in the Guide to Community Preventive Services. American Journal of Preventive Medicine. 18, Exponent, (2006). Section 23 Human Health Assessment.

Acknowledgments Dr. William Bailey Meghan Wagner Exponent Dr. Sat Bhattacharya Harlem Children’s Society Thank you all for listening!