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A systematic review and meta-analysis suggested the relative risk per Gy increased for all cardiovascular disease and for the four major subtypes of cardiovascular disease.
Exposure to low doses of ionizing radiation was linked to an extra lifetime risk of developing cardiovascular disease (CVD), according to the results of a recent systematic review.1
The review of approximately 15,000 studies produced 93 non-overlapping studies and suggested modest, but significantly increased, excess lifetime risk of 2.3 to 3.9 deaths per 100 people exposed to one Gy of radiation.
“The study suggests that radiation exposure, across a range of doses, may be related to an increased risk of not just cancer, as has been previously appreciated, but also of cardiovascular diseases,” said Andrew Einstein, MD, PhD, senior study author, Columbia University Vagelos College of Physicians and Surgeons.2 “It should not steer people away from receiving radiation if necessary – in fact many medical uses of radiation are lifesaving – but it underscores the importance of ensuring that radiation is used appropriately and kept as low as reasonably achievable.”
The systematic review and meta-analysis researched the risk of radiation associated CVD observed in therapeutically or diagnostically exposed cohorts. For the analysis, investigators further examined groups exposed to generally lower levels of radiation dose (with maximum dose <0.5 Gy) or low dose rate (<5 mGy/h). The systematic review used PubMed/Medline, Embase, Scopus, and Web of Science’s Core Collection to systematically search literature with no limits applied in October 2022, but investigators excluded animal studies and those without an abstract.
Four major subtypes of CVD determined a priori were used: ischemic heart disease, heart disease apart from ischemic heart disease, cerebrovascular disease, and all other types of CVD. As well as these four outcome categories, investigators additionally looked for information on overall CVD. In the analysis, the basis for estimation of radiation risk is the value of excess relative risk per unit of effective dose (excess relative risk per Sv) or absorbed dose (excess relative risk per Gy) of radiation exposure.
Upon analysis, in 93 studies, the relative risk per Gy increased for all CVD (excess relative risk per Gy, 0.11; 95% confidence interval [CI], 0.08 to 0.14) and for the four major subtypes of CVD. The investigative team noted interstudy heterogeneity (P <.05 for all endpoints but other heart disease), potentially a result in interstudy variation in unmeasured confounders or effect modifiers. It was markedly reduced if investigators restricted attention to higher quality studies or those at moderate doses (<0.5 Gy) or low dose rates (<5 mGy/h).
According to the analysis, for ischemic heart disease and all CVD, the risks were larger per unit dose for lower doses, suggesting an inverse dose effect, and for fractionated exposures, suggesting an inverse dose fractionation effect. Estimated risks of mortality from CVD were dominated by cerebrovascular disease (around 0.94- 1.26% per Gy), with the next largest contribution from ischemic heart disease (around 0.30-1.20% per Gy), based on the data.
Moreover, the population based excess absolute risk estimates for radiation exposure induced death for all CVD range from 2.33% per Gy (95% CI, 1.69% to 2.98%) for England and Wales to 3.66% per Gy (95% CI, 2.65% to 4.68%) for Germany. Einstein and colleagues noted these data largely reflect the underlying risk of CVD mortality.
The investigative team indicated the need for more research to determine the exact increased excess lifetime risk of heart disease from lower doses of radiation.
“The effect of lower doses of radiation on the heart and blood vessels may have been underestimated in the past,” Einstein said.2 “Our new study suggests that guidelines and standards for protection of workers exposed to radiation should be reconsidered, and efforts to ensure optimal radiation protection of patients should be redoubled.”