Low-dose radiation linked to increased lifetime risk of heart disease

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Exposure to low doses of ionizing radiation is associated with a modest increase in the risk of heart disease, finds an analysis of the latest evidence published by the BMJ today.

The researchers say these findings “have implications for patients undergoing radiation exposure as part of their medical care, as well as policymakers involved in managing radiation risks to radiation workers and the public.”

A related editorial suggests that these risks “must now be carefully considered in radiation protection in medicine and elsewhere.”

It is well known that high-dose radiation exposure can damage the heart, but strong evidence linking low-dose radiation to heart disease (eg radiation dose distribution from radiotherapy or work in the nuclear industry) are less clear.

To address this knowledge gap, an international team of researchers examined scientific databases for studies evaluating associations between a variety of cardiovascular diseases and radiation exposure (mainly radiotherapy and occupational exposures).

They excluded non-informative datasets or those that largely replicated others, leaving 93 studies, mostly published within the last decade, eligible for analysis. These studies covered a wide range of doses, short and long exposures, and assessed the frequency (incidence) and mortality of various types of vascular disease.

After taking into account other important factors, such as age at exposure, the researchers found consistent evidence for a dose-dependent increase in cardiovascular risks across a wide range of radiation doses.

For example, the relative risk per gray (Gy) was increased for all cardiovascular disease and for specific types of cardiovascular disease, and there was a higher relative risk per unit dose in the lower dose ranges (less than 0.1 Gy) , and also for lower dose rates (multiple hourly exposures in years).

At the population level, absolute excess risks ranged from 2.33% per Gy for a current population of England and Wales to 3.66% per Gy for Germany, largely reflecting the underlying cardiovascular disease mortality rates in these populations.

This equates to a modest but significantly increased lifetime excess risk of 2.3-3.9 cardiovascular deaths per 100 people exposed to one Gy of radiation, the authors explain.

Substantial variation was found between studies, although this was significantly reduced when the authors restricted their analysis to higher quality studies or those with moderate doses (less than 0.5 Gy) or low dose rates (less than 5 mGy/h).

The authors suggest that the mechanisms for these cardiovascular effects are not well understood, even at high doses.

They also acknowledge that few studies have evaluated the potential modifiable effects of lifestyle and medical risk factors on radiation risk, particularly major modifiable risk factors for cardiovascular disease such as smoking, obesity, diabetes, high blood pressure, and cholesterol. high, and say that further research is needed in this area.

In conclusion, they say their findings support an association between acute high-dose and (to a lesser extent) chronic low-dose radiation exposure and most types of cardiovascular disease and suggest that “radiation damage may was significantly underestimated, implying that low-dose radiation protection and optimization must be rethought.”

This view is supported by Professor Anssi Auvinen at the University of Tampere in Finland in a related editorial, who points out that while there remain inconsistencies and gaps in the evidence linking vascular disease to low-dose radiation exposure, “the evidence for cardiovascular disease will soon will have to be added to the existing list of health hazards caused by radiation.”

This will include the revision of concepts and standards in radiological protection, while stricter standards for justification and optimization, especially for high-dose procedures, will have to be considered, he explains.

Their implementation will also require training to improve awareness, knowledge and understanding of risks associated with specific procedures and cumulative exposure, as well as risk communication to patients and the public, he concludes.

More information: Ionizing radiation and cardiovascular disease: systematic review and meta-analysis, The BMJ (2023). DOI: 10.1136/bmj-2022-072924

Journal information: British Medical Journal (BMJ)