Standardized Incidence Ratio and Standardized Mortality Ratio of Malignant Mesothelioma in a Worker Cohort Using Employment Insurance Database in Korea

Our plain-English summary of Standardized Incidence Ratio and Standardized Mortality Ratio of Malignant Mesothelioma in a Worker Cohort Using Employment Insurance Database in Korea, by E.A. Kim (International Journal of Environmental Research and Public Health, 2021).

The study

• Author: E.A. Kim
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;18(20)
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma is one of the appropriate indicators for assessing the carcinogenic effects of asbestos. This study compared the risk ratio of mesothelioma according to the industry in the worker cohort. A cohort was constructed using the Korean employment insurance system during 1995-2017, enrolling 13,285,895 men and 10,452,705 women. The standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were calculated using the indirect standardization method. There were 641 malignant mesotheliomas that occurred; the SIR was significantly higher than the general population (men 1.36, 95% confidence interval (CI) 1.24-1.48, women 1.44, 95% CI: 1.23-1.7). More than half (52.8%) of malignant mesothelioma cases occurred in the manufacturing (n = 240, 38.6%, SIR: men, 1.72, 95% CI: 1.37-2.15, women, 3.31, 95% CI: 1.71-5.79) and construction industries (n = 88, 14.2%, SIR: men, 1.54 95% CI: 1.33-1.78, women, 1.62 95% CI: 1.25-2.11). The accommodation and food service (men, 2.56 95% CI: 1.28-4.58, women 1.35, 95% CI: 0.65-2.48) and real estate (men 1.34, 95% CI: 0.98-1.83, women 1.95, 95% CI: 0.78-4.02) also showed a high SIR, indicating the risk of asbestos-containing materials in old buildings. The incidence of malignant mesothelioma is likely to increase in the future, given the long latency of this disease. Moreover, long-term follow-up studies will be needed.

In plain English

This retrospective cohort study followed 13,285,895 men and 10,452,705 women enrolled in Korea's employment insurance system from 1995 to 2017. It linked cancer and death registries to find malignant mesothelioma. Workers were assigned to their longest-held industry and compared with the general Korean population. Mesothelioma was diagnosed in 480 men and 141 women. Incidence was significantly higher than in the general population (SIR 1.36, 95% CI 1.24–1.48, men; 1.44, 1.23–1.7, women). Mesothelioma mortality was not significantly different (SMR 0.88, 0.77–1.01, men; 0.95, 0.73–1.24, women). Incidence was significantly raised in construction (men 1.72, 1.37–2.15; women 3.31, 1.71–5.79) and manufacturing (men 1.54, 1.33–1.78; women 1.62, 1.25–2.11). For men in accommodation and food service, Table 2 reported a significant 2.56 (1.28–4.58). Table 4 assigned 2.56 to accommodation alone and 2.10 (1.05–3.75) to the combined industry. Real estate ratios were raised but not statistically significant. The author concluded that risk was high in known asbestos industries and also in lodging and real estate, possibly from asbestos in old buildings. The author noted an average follow-up of only eight to nine years and possible industry misclassification.

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: Retrospective cohort study using linked national databases. Standardized incidence and mortality ratios were calculated by indirect standardization against the general population.
• Who was studied: All workers enrolled in Korean employment insurance from 1 July 1995 to 31 December 2017: 13,285,895 men and 10,452,705 women. The system covers about 48.5% of Korean workers.
• Exposure: Asbestos exposure was not measured directly. Workers were classified by the industry (Korean Standard Industry Code) in which they had worked longest. An asbestos job-exposure matrix could be applied to only a small share of the cohort.
• Main results:
  • Malignant mesothelioma was diagnosed in 480 men and 141 women in the cohort. Deaths from it numbered 216 men and 54 women.
  • Whole cohort compared with the general population: SIR 1.36 (95% CI 1.24–1.48) for men and 1.44 (95% CI 1.23–1.7) for women. Both were statistically significant.
  • Whole cohort mortality: SMR 0.88 (0.77–1.01) for men and 0.95 (0.73–1.24) for women. These were lower than the general population, but the difference was not statistically significant.
  • Manufacturing, men: 183 cases, SIR 1.54 (95% CI 1.33–1.78), statistically significant. Table 2 gives women in manufacturing 57 cases and SIR 1.62 (1.25–2.11), also significant.
  • Construction, men: 76 cases, SIR 1.72 (95% CI 1.37–2.15). Construction, women: 12 cases, SIR 3.31 (95% CI 1.71–5.79). Both were statistically significant.
  • Men in construction had a statistically significantly raised mesothelioma mortality: SMR 1.4 (1.04–1.89).
  • Men in accommodation and food service: Table 2 and the results text give 11 cases and SIR 2.56 (95% CI 1.28–4.58), statistically significant. However, Table 4 and its text assign 2.56 (1.28–4.58) to the accommodation subdivision (KSIC 55) alone, and give 2.10 (1.05–3.75) for the combined accommodation and food service division. Women in this industry: SIR 1.35 (95% CI 0.65–2.48), not significant.
  • Real estate: men SIR 1.34 (95% CI 0.98–1.83, 39 cases) and women SIR 1.95 (95% CI 0.78–4.02). Neither was statistically significant.
• The authors' conclusion: The author concluded that mesothelioma risk was high in previously known asbestos-risk industries, and also in the lodging and real estate management industries. The author suggested the latter might relate to asbestos-containing materials in old buildings, and expected incidence to increase given the disease's long latency. The author also raised the possibility that past asbestos-related work was overlooked for lack of occupational information.
• Limitations the authors state:
  • The average follow-up of eight to nine years is too short to show mesothelioma trends, given a latency of more than 40 years.
  • Classifying workers by their longest-held industry may misclassify exposure, because that industry is not necessarily the one with the highest exposure.
  • The employment insurance database does not represent the entire Korean workforce. It excludes public officials, military personnel and others, and business owners and self-employed people join only voluntarily.
  • Because job information was lacking, the asbestos job-exposure matrix could classify only 8.3% of men and 12.5% of women. Past asbestos-related work may therefore have been overlooked.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Standardized Incidence Ratio (SIR), standardized mortality ratio (SMR), Malignant Mesothelioma, Carcinogenic, Mesothelioma, confidence interval, Asbestos-Containing Material (ACM), Latency.

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