Understanding the Impact of Study Design on Results:

A Comparison of Two Radioactive Iodine Studies in Washington State



Speakers:                   Steven G Inserra, MPH REHS

Epidemiologist, ATSDR, Div of Health Studies


Caroline Cusack, MSPH

Epidemiologist, ATSDR, Div of Health Studies


Level of Knowledge:  Multi-Level




The purpose of this presentation is to recognize and understand the impact of study design and methodology for assessing burden of environmental-related disease. We reviewed and compared study publications that evaluated thyroid disease burden in a region of Washington State from the mid-1990s and forward. Radioactive iodine was released into the air from the Hanford Nuclear Site in Washington from the 1940s through the 1970s. Because iodine-131 concentrates in the human thyroid when inhaled or consumed, various investigators studied possible iodine exposure effects using population-based studies. The compared studies arrived at seemingly different conclusions regarding thyroid disease prevalence levels and risk from environmental exposures. These results and the communication thereof may generate questions from the public and officials. To bring clarity to this quandary, this presentation will review the studies' methodologies to better understand their impact on overall results. We will highlight conceptual constructs-study design, time period, case ascertainment, sampling strategy, data sources, and analysis-for the purpose of improving professional understanding. Knowledge imparted through this presentation may be applied to future reports and publications for both advancing professional practice and improving health communications with scientists, policy makers, and the public.


Learning Objectives:


  1. Understand the potential for similarities and differences in study results from the same regional population studied
  2. Understand an approach to review and compare study methodologies
  3. Gain a better understanding of the impact of research methodologies to improve health communications with the public and health officials