Low Levels of Radiation Exposure Could Increase Risk of Heart Disease, Researchers Warn

Researchers were surprised to find an inverse dose effect, meaning the risks of cardiovascular disease actually increased at very low doses of radiation.

Frequent exposure to low doses of radiation from cancer treatments, CT scans, and some jobs in the healthcare, aviation and nuclear industries, may increase the risk of heart disease, according to the findings of a new study.

Research has long indicated exposure to ionizing radiation at high doses can increase a person’s likelihood of developing cardiovascular disease. However, a new report published this month in the medical journal The BMJ suggests that the heart disease risks may be caused by much lower doses of radiation than previously believed.

Researchers from the University of Las Vegas (UNLV) School of Integrated Health Sciences conducted a meta-analysis of 93 relevant studies focusing on the effects of ionizing radiation.

The studies examined radiation exposure at varying levels, including radiation exposure from cancer treatment, exposure from common medical tests like CT scans, and exposure from workplace environments in nuclear industries and the medical industry. The researchers looked at the effects of radiation exposure and rates of the four types of cardiovascular disease, defined as ischemic heart disease, cerebrovascular disease, other heart disease, and other cardiovascular disease.

According to the findings, the researchers found what is called an inverse dose effect for both ischemic heart disease and cardiovascular disease, meaning that the risk of those two ailments actually increased at lower doses of radiation exposure.

The researchers determined the risk of cardiovascular disease was higher when the maximum radiation dose was 0.5 Gray units (Gy) or less. But they also noted that high doses of radiation, above those commonly considered safe, were also linked to increased cardiovascular disease as well.

Gray units have replaced rads as a measure of radiation exposure. One Gray unit equals 100 rads. Exposure to five Gy at once is considered lethal, and usually causes death in about 14 days.

“Our systematic review and meta-analysis supports an association between acute high dose and chronic low dose radiation exposure and most types of cardiovascular disease. Low dose and low dose rate exposure tend to be associated with higher risk per unit dose,” the researchers concluded. “Our findings suggest that radiation detriment might have been significantly underestimated, implying that radiation protection and optimisation at low doses should be rethought. The possible mechanisms for risk at low doses and low dose rates are, in contrast to the situation at higher doses and dose rates, relatively poorly understood, thus underscoring a crucial need for further research in this area.”

Radiation Exposure Risks Not Limited to Healthcare

The risk researchers saw in the study applies not only to patients treated for cancer, or the general population undergoing CT scans, but also those working in the nuclear weaponry and energy industries, transcontinental pilots, healthcare workers, astronauts and any member of the population exposed to any level of radiation beyond that of the general public.

Researchers speculate radiation may cause inflammation in the body, but specifically the heart, which leads to changes in the immune response that may cause heart disease.

The researchers recommend people who face an increased risk of cardiovascular disease from radiation exposure of any kind should work with their doctor to monitor and treat the condition if necessary, as well as addressing any behavioral risk factors that could worsen the disease.