Indoor Radon Concentrations and Hematologic Traits in the Women’s Health Initiative

Background: We examined radon’s association with the complete blood count and leukocyte differential to better understand radon-related risks of stroke and myocardial infarction (MI) previously observed in the Women’s Health Initiative (WHI). Methods: We conducted a repeated measures analysis in this prospective cohort of post-menopausal women enrolled in 1993-1998 and examined at 5 visits over 19 years in 40 US clinical centers (n=154,630). We estimated indoor radon concentrations (pCi/L) at time-varying, geocoded addresses of participants (1993-2013) by linking them to the US Geological Survey Radon Index (1993) zoned by US Environmental Protection Agency Action Levels. We estimated covariate-adjusted, longitudinal associations of radon concentrations with complete blood count components using linear mixed-effects models. In a subset (n=6,313), we evaluated cross-sectional associations with the complete blood count differential using multivariate compositional data analysis. Results: At 2–4 and >4 pCi/L, adjusted mean (95% confidence interval) leukocytes were 48 (33, 63) and 78 (58, 98) cells/μL lower than at <2 pCi/L, while platelets, hematocrit, and hemoglobin were higher: 315 (-280, 910) and 2,033 (1,248, 2,818) cells/μL; 0.27% (0.24%, 0.30%) and 0.23% (0.19%, 0.27%); and 0.09 (0.08, 0.10) and 0.09 (0.07, 0.10) g/dL. Nonlinear spline models of the Radon Index revealed similar associations. Lymphocyte percentages were lower and other percentages were higher at higher (>4 pCi/L) vs. lower (<2 pCi/L) radon concentrations in nonlinear compositional data analysis. Conclusion: The radon-related cardiovascular implications of these modest, pro-thrombotic, myeloid shifts in the complete blood count/differential among postmenopausal women in the WHI remain unknown.