Occupational exposure to asbestos and cardiovascular related diseases: A meta-analysis

Our plain-English summary of Occupational exposure to asbestos and cardiovascular related diseases: A meta-analysis, by Y. Rong, X. Luo, Z. Zhang, et al (Preventive Medicine Reports, 2015).

The study

• Authors: Y. Rong, X. Luo, Z. Zhang, X. Cui, Y. Liu, W. Chen
• Journal: Preventive Medicine Reports
• Published: 2015;2:920-6
• Type of article: Review
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos has become one of the leading causes of death among occupational workers in the world. The association between asbestos and cardiovascular disease is less reported. We performed a meta-analysis to quantify the association between asbestos exposure and the mortality of cardiovascular related diseases. We performed a systematic review in the PubMed database before December 2014. All cohort studies citing the standardized mortality ratio (SMR) of cardiovascular related diseases in workers exposed to asbestos were collected. We then calculated the pooled standardized mortality ratios of such diseases. Sixteen studies were included. The combined results from all studies indicated the pooled SMR estimate for cardiovascular related diseases was 1.11 (95% CI, 1.01-1.22). This meta-analysis showed that asbestos exposure significantly increased the risk of cardiovascular related diseases in exposed workers.

In plain English

This was a meta-analysis. The authors searched PubMed for studies published before December 2014 and combined 16 cohort studies that reported standardized mortality ratios (SMRs) for cardiovascular related diseases among workers exposed to asbestos. The studies came from Europe, North America, South Africa, Australia and China. They covered mining, textile manufacturing, cement production and construction. Across all studies the pooled SMR was 1.11 (95% CI, 1.01–1.22). Results varied widely between studies. By fiber type, pooled SMRs were 1.23 (95% CI, 1.07–1.41) for chrysotile, 1.26 (95% CI, 1.02–1.56) for amphibole and 0.80 (95% CI, 0.74–0.86) for crocidolite. By disease, the pooled SMR was 4.13 (95% CI, 1.55–10.98) for pulmonary heart disease and 1.04 (95% CI, 0.82–1.32) for ischemic heart disease. The authors concluded that asbestos exposure significantly increased the risk of cardiovascular related diseases in exposed workers. They noted limitations. The analysis could not take account of smoking, diet or other non-work risk factors. Classifying exposure by job title may have put some workers in the wrong exposure group. Other workplace hazards could have made the asbestos risk look larger than it was.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Meta-analysis of published cohort studies reporting standardized mortality ratios (SMRs), using a random-effects model
• Who was studied: 16 cohort studies of asbestos-exposed workers, found in a PubMed search before December 2014: nine from European countries, four from North America, and one each from China, Australia and South Africa
• Exposure: Occupational asbestos exposure: chrysotile, amphibole, amosite, crocidolite or mixed asbestos, in mining, textile manufacture, cement production and construction
• Main results:
  • All studies combined: pooled SMR for cardiovascular related diseases among asbestos-exposed workers was 1.11 (95% CI, 1.01–1.22), which was statistically significant
  • There was significant heterogeneity among the studies (I2 = 93.5%)
  • No evidence of publication bias was found (Egger test P = 0.36; Begg test P = 0.83)
  • Workers exposed to chrysotile: pooled SMR 1.23 (95% CI, 1.07–1.41). Workers exposed to amphibole: pooled SMR 1.26 (95% CI, 1.02–1.56)
  • Workers exposed to crocidolite: pooled SMR 0.80 (95% CI, 0.74–0.86)
  • Workers exposed to mixed asbestos: pooled SMR 0.81 (95% CI, 0.6–1.08)
  • By region: pooled SMR 0.88 (95% CI, 0.75–1.02) for European studies, 1.20 (95% CI, 1.09–1.32) for USA workers, and 1.75 (95% CI, 1.17–2.60) for other countries
  • USA workers: pooled SMR 1.20 (95% CI, 1.09–1.32)
  • Other countries (South Africa, Australia, China): pooled SMR 1.75 (95% CI, 1.17–2.60)
  • By industry: textile workers' pooled SMR of 1.41 (95% CI, 1.16–1.70) was significantly higher than cement workers' 0.82 (95% CI, 0.70–0.98)
  • By disease: pooled SMRs were significantly elevated for pulmonary heart diseases, 4.13 (95% CI, 1.55–10.98), and other heart diseases, 1.32 (95% CI, 1.14–1.53)
  • Pooled SMRs were 0.99 (95% CI, 0.88–1.11) for circulatory diseases, 0.99 (95% CI, 0.86–1.14) for all heart diseases, and 1.04 (95% CI, 0.82–1.32) for ischemic heart diseases
  • After excluding the two studies contributing most to variation between studies (Musk et al. 2008 and Menegozzo et al. 2011), the pooled SMR was 1.17 (95% CI, 1.07–1.28)
• The authors' conclusion: The authors concluded that asbestos exposure significantly increased the risk of cardiovascular related diseases in exposed workers
• Limitations the authors state:
  • A number of the included studies lacked details of exposure assessment
  • Where studies used job titles to classify exposure, misclassification is possible
  • Differing definitions of exposure duration and latency prevented a unified evaluation of dose-response
  • Questionnaire-based exposure information (Harding et al., 2012) may be affected by individual biases
  • Other unknown occupational hazards may not have been accounted for and could overestimate the asbestos risk
  • The analysis could not assess non-occupational risk factors such as smoking, living habits, diet, alcohol use or medications
  • Some studies were left out because they did not report cardiovascular outcomes or reported SMRs without confidence intervals
  • There was significant heterogeneity among the included papers

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Meta-Analysis, Asbestos Exposure, Systematic Review, standardized mortality ratio (SMR).

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