The Correlation Between Ionising Radiation and Cardiovascular Disease

BMJ 2023; 380 doi: https://doi.org/10.1136/bmj-2022-072924 (Published 08 March 2023)

Cite this as: BMJ 2023;380:e072924

Introduction

Cardiovascular disease (CVD) is the leading cause of death globally. Several factors such as overall health, stress, smoking, age, genetics and diabetes cause an increase in total and low density lipoprotein, which is classified as “bad” cholesterol. Cardiovascular disease (CVD), specifically coronary heart disease, is caused by the buildup of this bad cholesterol in the arteries, causing a blockage known as atherosclerosis.

Radiotherapy is a type of cancer treatment that uses ionising radiation to shrink or kill tumours with external beams of light focused at particular tumour cells in the body, destroying their ability to divide. This treatment is often administered alongside chemotherapy.

Recently, it has been discovered that environmental factors and exposure to radiotherapy to the heart may cause or increase risk of cardiovascular disease, which affects the heart and blood vessels, including the coronary artery. The objective of this study was to identify whether there was a direct link between ionising radiation and cardiovascular disease. Over the years, radiation dosage for cancer patients has decreased, and doses tend to be lower for diseases other than cancer. This allowed for a comparison between CVD in older patients that underwent radiotherapy as children against people who recently underwent the same.

Prior Research

Prior to this study, it was known that exposure to high-dose ionising radiation during radiotherapy had a damaging effect on the heart. According to the ICRP (the International Commission on Radiological Protection), survivors of childhood cancers who were given a radiotherapy dosage over 15 Gy (Gray, the unit of measurement of ionising radiation dose) had an increased risk of CVD mortality. Additionally, there was a life span study undertaken of the Japanese atomic bomb survivors which provided evidence of an increased risk of cardiovascular disease. However, data regarding the extent of the effect of low doses of radiation on the risk for CVD has been uncertain due to varying rates of radiation exposure during therapy over the years. Evidence has emerged suggesting that there is an effect, however mild, but it was deemed inconclusive.

Outcome

The study proved a correlation between radiation exposure and most types of cardiovascular disease. While conducting the study, scientists chose four outcome categories, which were the four major types of cardiovascular disease. Coronary heart disease, general heart disease, cerebrovascular disease, and all other variations of CVD. Factors considered included the maximum radiation dose, dose frequency and age at exposure. As it was known that high dose radiotherapy had a detrimental effect on the heart, the study focused on the effect of low doses. A major limitation of this study was heterogeneity, or the diversity of populations across nations (essentially the varying environmental factors which could contribute to CVD), which made it hard to determine a causal relationship between low dose radiotherapy and cardiovascular disease. It was discovered that cerebrovascular disease had the greatest effect on mortality, followed by coronary heart disease. Results were collated using various models, taking into consideration the years lost from one’s lifespan due to CVD per exposure to ionising radiation. The conclusion to this study was that patients who have undergone or are undergoing radiotherapy must modify other contributing factors to cardiovascular disease, such as lifestyle and stress factors to reduce their risk of CVD.

By Vedika Sabnavis

Works cited

US EPA, OAR. “Radiation Therapy.” Www.epa.gov, 26 Nov. 2018, www.epa.gov/radtown/radiation-therapy#:~:text=Radiation%20therapy%20uses%20ionizing%20radiation.

Little, Mark P., et al. “Ionising Radiation and Cardiovascular Disease: Systematic Review and Meta-Analysis.” BMJ, vol. 380, Mar. 2023, p. e072924, https://doi.org/10.1136/bmj-2022-072924.

‌Stewart, F. A. “Mechanisms and Dose-Response Relationships for Radiation-Induced Cardiovascular Disease.” Annals of the ICRP, vol. 41, no. 3-4, Oct. 2012, pp. 72–79, https://doi.org/10.1016/j.icrp.2012.06.031. Accessed 14 May 2020.