Exposure to low-dose radiation in occupational settings and ischaemic heart disease: a systematic review and meta-analysis

Abstract

Ionising radiation is a human carcinogen, but the evidence is less clear that exposure to low-dose ionising radiation (LDIR) increases the risk of adverse cardiovascular outcomes. We synthesised the literature of chronic occupational exposure to LDIR and cardiovascular disease, particularly for ischaemic heart disease (IHD).The literature search was conducted using three databases including studies published between 1990 and 2022. A quality assessment of the studies was completed using the Office of Health and Assessment and Translation Risk of Bias Rating Tool. We conducted meta-analyses for IHD mortality using random effects models using measures of excess relative risk per sievert (ERR/Sv) obtained from internal cohort comparisons, as well as with standardised mortality ratios (SMRs) from external cohort comparisons.We identified 2189 articles, and of these, 26 provided data on IHD and were retained. Most studies were classified as having a 'moderate' level of risk of bias. Fourteen and 10 studies reporting external radiation doses were included in meta-analyses using SMR and ERR/Sv, respectively. The meta-summary SMR was 0.81 (95% CI 0.74 to 0.89) with evidence of reduced risk but high heterogeneity across studies. For internal cohort measures, the summary ERR/Sv for a lagged exposure of 10 years was 0.10 (95% CI 0.01 to 0.20) with low heterogeneity. The subgroup analysis by lagged exposure time showed the strongest association were for the 15 and 20 years lag.Our findings suggest that occupational exposure to LDIR increases the risk IHD mortality and highlight the relevance of internal cohort comparisons.

Keywords: Cardiology; Occupational Health; Radiation, Ionizing.

Figure 1

PRISMA diagram for the systematic review on occupational low-dose radiation exposure and ischaemic heart disease. *Electronic databases. IHD, ischaemic heart disease; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analysis.

Figure 2

Summary of OHAT risk of bias assessment (data labels equate to number of studies). National toxicology Programme. OHAT risk of bias tool (internet). 2015. Available from: https://ntp.niehs.nih.gov/ntp/ohat/pubs/riskofbiastool_508. OHAT, Office of Health and Assessment and Translation.

Figure 3

Meta-analysis of association between ischaemic heart disease mortality and low-dose occupational radiation exposure expressed as standardised mortality ratio (SMR) with comparisons to general population.

Figure 4

Meta-analysis of the association between ischaemic heart disease mortality and low-dose occupational radiation exposure for external dose expressed as excess of relative risk per sievert (ERR/Sv) by subgroups of latency exposure. INWORKS, International Nuclear Workers Study.