Occupational exposure to silica and risk of heart disease: a systematic review with meta-analysis

Objective To search for evidence of the relationship between occupational silica exposure and heart disease.

Design A systematic review and meta-analysis.

Background Growing evidences suggest a connection between occupational silica exposure and heart disease; however, the link between them is less clear.

Data sources PubMed, ScienceDirect, Springer and EMBASE were searched for articles published between 1 January 1995 and 20 June 2019. Articles that investigated the effects of occupational silica exposure on heart disease risk were considered.

Study selection We included cohort studies, including prospective, retrospective and retro-prospective studies.

Data extraction and synthesis We extracted data by using a piloted data collection form and conducted random-effects meta-analysis and exposure-response analyses. The meta-relative risk (meta-RR), a measure of the average ratio of heart disease rates for those with and without silica exposure, was used as an inverse variance-weighted average of relative risks from the individual studies. The Newcastle-Ottawa Quality assessment Scale about cohort studies was used for study quality assessment.

Outcome measure We calculated heart disease risks of pulmonary heart disease, ischaemic heart disease and other heart diseases.

Results Twenty cohort articles were included. Results suggest a significant increase of overall heart disease risk (meta-RR = 1.08, 95% CI = 1.03, 1.13). Stronger evidences of association with pulmonary heart disease were found through both categories of heart disease risk estimate (meta-RR = 1.24, 95% CI = 1.08, 1.43) and exposure-response analyses (meta-RR = 1.39, 95% CI = 1.19, 1.62). Moreover, our subgroup analyses revealed that the statistical heterogeneity among studies could be attributed mainly to the diversities of reference group, occupation and study quality score.

Conclusions Silica-exposed workers have increased risk of overall heart disease, especially pulmonary heart disease. While further research is needed to better clarify the relationship between occupational silica exposure and ischaemic heart disease.