Residential radon exposure and stroke risk: the REGARDS study

Stroke remains a major cause of death and disability in the U.S. Identifying modifiable risk factors to develop effective prevention is the best strategy for reducing the burden of this disease. Racial and geographic variations in stroke mortality has been observed in the U.S. for decades. However, the reasons for these variations are still unclear. The impact of radon exposure in relation to human health has been increasingly recognized. Radon is a colorless, odorless, radioactive gas, formed through the radioactive decay of radium- 226, which enters homes, and other buildings, through cracks and penetrations in the building substructure. Radon has been classified as a human lung carcinogen by the International Agency for Research on Cancer since 1988. Recently, some studies conducted in countries outside the U.S. have linked radon, even at low levels of exposure, to the risk of stroke. In the U.S., county-level radon exposure has been associated with elevated mortality from cardiovascular and metabolic diseases. The overarching goal of this project is to examine the association between radon exposure and stroke risk and to investigate whether geographic variation of radon concentration is related to the distribution of stroke rate in the U.S. Specifically, we will examine radon exposure at both county- and household-level in relation to the risk of ischemic stroke. In addition, we will explore the underlying mechanisms by linking radon exposure to blood pressure, hypertension, lipid profile, and hemostatic and inflammatory biomarkers. Radon exposure is rising steadily within the modern North American residential environment. The proposed study will be the first to assess radon exposure and stroke risk in the U.S. general population, including both male and female African Americans and Caucasians. Since randomized clinical trial on radon exposure is not feasible, findings from this project will provide insights into the racial and geographic variations of stroke rate in the U.S. and possibly identify a potential modifiable risk factor for stroke.