Radon, a naturally occurring radioactive gas produced when metals like uranium or radium break down in rocks and soil, is a known cause of lung cancer. Now new research has found exposure to high levels of this indoor air pollutant is associated with an increased risk of another condition in middle age to older female participants with ischemic stroke.
The study is published in the January 3, 2024, online issue of Neurology, the medical journal of the American Academy of Neurology. Ischemic stroke is caused by a blockage of blood flow to the brain and is the most common type of stroke.
The condition, called clonal hematopoiesis of indeterminate potential (CHIP), develops when some hematopoietic stem cells, the building blocks for all blood cells, undergo genetic mutations as a person ages. Cells with such mutations replicate more quickly than cells without them. Previous research has shown people with CHIP may have a higher risk of blood cancers like leukemia and cardiovascular disease including stroke.
The study involved 10,799 female participants with an average age of 67. Approximately half of participants had a stroke or blood clots.
To determine radon exposures, researchers linked participants’ home addresses to U.S. Environmental Protection Agency (EPA) data on average indoor radon concentrations by county. The EPA recommends that average indoor radon concentrations do not exceed four picocuries per liter (pCi/L).
Participants were divided into three groups. The highest group lived in areas where average radon concentrations were more than four pCi/L. The middle group lived in areas with average concentrations between two and four pCi/L. The lowest group lived in areas with average concentrations of less than two pCi/L.
Researchers then used genetic testing to determine which participants had mutations typical of CHIP. Researchers found that 9.0% of participants living in areas with the highest concentration of radon had CHIP, compared to 8.4% those living in areas with medium concentrations and 7.7% of those living in areas with the lowest concentrations.
After adjusting for factors such as age, education, race and ethnicity, researchers found participants with ischemic stroke living in areas with the highest concentrations of radon had a 46% increased risk of CHIP, while those living in areas with medium concentrations had a 39% increased risk compared to those living in areas with the lowest concentrations of radon. Risk was not increased in participants without stroke.
