A mortality cohort study of seamen in Italy

Our plain-English summary of A mortality cohort study of seamen in Italy, by E. Rapiti, E. Turi, F. Forastiere, et al (American Journal of Industrial Medicine, 1992).

The study

• Authors: E. Rapiti, E. Turi, F. Forastiere, P. Borgia, P. Comba, C.A. Perucci, O. Axelson
• Journal: American Journal of Industrial Medicine
• Published: 1992;21(6):863-72
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A total of 2,208 male subjects, enrolled as merchant marine seamen at the Civitavecchia (Italy) harbor from 1936 to 1975 were followed up through 1989 in order to evaluate their mortality experience. Available information about the number of sailings made it possible to divide subjects into two subgroups: 948 workers with at least one sailing (cohort A) and 1,260 with no reported sailing (cohort B). Fewer than expected overall deaths were observed in both cohorts (cohort A: SMR = 0.83; cohort B: SMR = 0.81), mainly due to a lower mortality from circulatory, respiratory, and digestive diseases. Lung cancer deaths were significantly increased in cohort A (O = 30, SMR = 1.71, 95% CI = 1.15-2.44), whereas no excess was observed in cohort B (O = 6, SMR = 0.57, 95% CI = 0.21-1.26). Among subjects employed aboard ship, a trend in SMRs for lung cancer increasing with duration of employment was observed. Furthermore, three neoplasms of other parts of the respiratory system (including one mesothelioma) were detected in cohort A (SMR = 5.87), and one in cohort B. The study substantiates an increased risk of respiratory cancer among subjects with an occupational history of sailing; past exposure to asbestos and to other environmental carcinogens aboard could be implicated.

In plain English

This retrospective mortality cohort study followed men registered as merchant marine seamen at the harbor office of Civitavecchia, Italy, between 1936 and 1975. Follow-up ran from 1965 through 1989. The authors split the men into 948 with at least one recorded sailing (cohort A) and 1,260 with none (cohort B). They compared deaths with numbers expected from regional (Latium) death rates. Overall deaths were lower than expected in both groups (SMR 0.83 and 0.81). In cohort A, 30 lung cancer deaths occurred against 17.5 expected (SMR 1.71, 95% CI 1.1 to 2.5). Cohort B showed no lung cancer excess (SMR 0.57). Compared with cohort B, cohort A had an age-adjusted lung cancer rate ratio of 3.09 (95% CI 1.28 to 7.45), and lung cancer in cohort A rose with duration of employment. One cohort A death, in a man who mainly worked as a stoker, was certified as mesothelioma and confirmed as pleural cancer. The authors concluded that seamen showed an increased respiratory cancer risk, possibly from asbestos exposure. They had no smoking data and no measurements of exposure on board.

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 mortality cohort study based on harbor-office registration records. Mortality was compared with regional (Latium) death rates, and the two cohorts were also compared with each other.
• Who was studied: All male seamen registered at the Civitavecchia (Latium, Italy) harbor office from 1 Jan. 1936 to 31 Dec. 1975. They were followed from 1965 (or later registration) to 31 Dec. 1989.
• Exposure: Recorded sailing on Italian ships: cohort A had at least one recorded sailing and cohort B had none. No measurements of asbestos or other on-board exposures were made, and no fiber type is named. The authors discuss asbestos from maintenance work or deteriorating insulation, exhaust gases, oil mists and solvents as possible exposures aboard.
• Main results:
  • Of 2,267 eligible seamen, 59 had died before 1965. The final cohorts were 948 men (cohort A) and 1,260 men (cohort B).
  • Overall mortality was lower than expected in both cohorts: SMR 0.83 in cohort A and 0.81 in cohort B.
  • Cohort A had 36 respiratory cancer deaths against 19.8 expected from regional data (SMR 1.81, 95% CI 1.3 to 2.5).
  • Cohort A had 30 lung cancer deaths against 17.5 expected (SMR 1.71, 95% CI 1.1 to 2.5 in the results text; the printed abstract gives 1.15 to 2.44).
  • Cohort B showed no lung cancer excess (SMR 0.57).
  • The age-adjusted lung cancer rate ratio for cohort A compared with cohort B was 3.09 (95% CI 1.28 to 7.45).
  • In cohort A, lung cancer mortality increased with duration of employment after adjusting for time since first registration (p for trend 0.006).
  • In cohort A, an SMR of 3.18 (p less than 0.01) was found among men with 30 or more years of both employment and time since registration.
  • Three deaths from cancers of other parts of the respiratory system, including one mesothelioma, occurred in cohort A (SMR 5.87). One such death occurred in cohort B.
  • Clinical record review confirmed pleural cancer only for the cohort A man whose death was certified as mesothelioma. He died in 1977 aged 60, had been a Navy stoker in 1937 to 1939, and sailed on merchant vessels, mainly as a stoker, from 1940 until 1971. The other two cohort A deaths appeared to be lung cancer involving the mediastinum.
  • Cohort B, the non-sailing group, showed a statistically significant excess of cancers of the lymphatic and hemopoietic tissues (SMR 2.62, 95% CI 1.1 to 5.2).
• The authors' conclusion: The authors concluded that the study indicated an increased risk of respiratory cancer among seamen, possibly because of asbestos exposure. They noted that other unrecognized respiratory carcinogens may also have played a role.
• Limitations the authors state:
  • Detailed occupational histories were not available, so cancer risks from previous jobs could not be ruled out.
  • There were no detailed data on exposures on board, which made it difficult to identify a specific cause of the lung cancer excess.
  • There were no smoking data, so confounding by smoking could not be excluded.
  • Some cohort B members may have sailed on foreign-flag ships, which were not recorded. The authors state this would bias results toward the null.
  • The full sailing history was not collected, so the true time spent aboard ship could not be estimated.
  • Using the regional population as the reference, the authors observed a strong healthy worker effect in both cohorts.

Topics

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

Medical terms in this study, explained in our Lexicon: Cohort Study, Merchant Marine, Lung Cancer, Neoplasm, Mesothelioma, Occupational History.

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