Fifty-year follow-up of mortality among a cohort of iron-ore miners in Sweden, with specific reference to myocardial infarction mortality

Abstract

Objectives: This study investigates both general mortality and mortality from myocardial infarction among men employed in iron-ore mines in Sweden.

Methods: The mortality of employees (surface and underground workers) at the iron-ore mines in Malmberget and Kiruna, Sweden was investigated. The study cohort comprised men who had been employed for at least 1 year between 1923 and 1996. The causes of death were obtained from the national cause of death register from 1952 to 2001. Indirect standardised mortality ratios (SMR) were calculated for four main causes. Mortality specifically from myocardial infarction was also analysed.

Results: 4504 deaths in the cohort gave an SMR for total mortality of 1.05 (95% CI 1.02 to 1.09). Mortality was significantly higher for lung cancer (SMR 1.73, 95% CI 1.52 to 1.97). There was an increased risk of injuries and poisonings (SMR 1.34, 95% CI 1.24 to 1.46) and respiratory diseases (SMR 1.14, 95% CI 1.00 to 1.28). There were 1477 cases of myocardial infarction, resulting in an SMR of 1.12 (95% CI 1.07 to 1.18). SMR was higher (1.35, 95% CI 1.22 to 1.50) for men aged ≤60 years than for those >60 years of age (1.06, 95% CI 1.00 to 1.13).

Conclusions: Mortality from myocardial infarction was higher than expected. There was also an increased risk of death from injuries and poisonings, lung cancer and respiratory diseases, as well as higher general mortality. Our findings support the results of previous studies that there is an association between working in the mining industry and adverse health outcomes.