umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Do physical workload or temperature characteristics in an outdoor workingenvironment explain deviating rates of mortality and incidental cancer? A cohort study based on iron-ore mining.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
Umeå University, Faculty of Medicine, Department of Radiation Sciences.
Umeå University, Faculty of Medicine, Department of Radiation Sciences.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
Show others and affiliations
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background A cohort study that examined iron ore mining found negative associations between cumulative working time employed underground and several severe outcomes. In this cohort study, and using the same group of miners, we examined whether heavy physical workload or the temperature characteristics represented by an outdoor working environment could explain these lower rates.

Method This study was based on a Swedish iron ore mining cohort consisting of 13000 workers employed between 1923 and 1998. Exposure was defined as cumulative employment time in heavy physical workload or outdoor work. Poisson regression models were used to generate smoothed estimates of standardized morbidity ratios and adjusted rate ratios, both models by cumulative exposure time. SMRs for different cohort subgroups were used to compare the occurrence of cerebrovascular disease mortality to the reference population.

Results The adjusted rate ratio between employment classified as outdoor work ≥25 years and short term outdoor work was 1.62 (95% CI 1.07–2.42). The subgroup underground work ≥15 years deviated most in occurrence of cerebrovascular disease mortality compared with the reference population: SMR (0.70 (95% CI 0.56–0.85)). No elevated rates were associated with cumulative employment time representing heavy physical workloads.

Conclusion Employment in temperature shifting outdoor environments was associated with elevated rates of cerebrovascular disease mortality. In contrast, work in tempered underground employment was associated with a protecting effect. Based on selected groups of mortalities, physically heavy workloads did not protect for mortality later in life.

Keyword [en]
Poisson regression, occupation, standardized mortality ratio, mortality, cancer incidence, cohort, mining
National Category
Environmental Health and Occupational Health
Research subject
Occupational and Environmental Medicine
Identifiers
URN: urn:nbn:se:umu:diva-81783OAI: oai:DiVA.org:umu-81783DiVA: diva2:658573
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2013-10-30Bibliographically approved
In thesis
1. Strategies for assessing health risks from two occupational cohorts within the domain of northern Sweden
Open this publication in new window or tab >>Strategies for assessing health risks from two occupational cohorts within the domain of northern Sweden
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Strategier vid utvärdering av hälsorisker baserade på två arbetarekohorter från norra Sverige
Abstract [en]

Background Studies based on a cohort design requires access to both subject-specific and period-specific information. In order to conduct an occupational cohort study, access to exposure information and the possibility and permission to link information on outcomes from other registers are generally necessary. The analysis phase is also aggravated by its added complexity because of the longitudinal dimension of the cohort’s data.This thesis aims at increasing the knowledge on hazards from work on fatalities and cancer within the domain of cohort studies on miners and metal refiners and to study the complexity of the analysis by discussing and suggesting analytical strategies.

Methods The study population for this thesis consisted of a cohort of 2264 blue-collar aluminium smelter workers (paper I) and a cohort of 13000 blue-collar iron-ore miners (papers II-IV), both followed for over 50 years. The outcomes were collected from the Swedish Cause of Death Register and the Swedish Cancer Register. The primary methods of analysis were either Standardized Morbidity Ratios (SMR) or internal comparisons based on Cox or Poisson regression modeling. In paper IV, a g-estimation based on an accelerated failure-time model was performed to estimate the survival ratio.

Results The results from paper I suggested that working as a blue-collar worker metal refiner was associated with increased rates of incidental lung cancer. Elevated rates among short term workers were observed for several outcomes. Paper I also showed that the choice of reference population when calculating SMR could influence the conclusions of the results. In paper II, several outcomes were elevated among the miners compared to the reference population from northern Sweden. However, no outcome except lung cancer was associated with cumulative employment time. The most recurrent pattern of the results was the negative association between cumulative employment time underground and several outcomes. The results from paper III showed that cumulative employment time working outdoors was associated with increased rates of cerebrovascular disease mortality. However, employment with heavy physical workloads did not explain the previously observed decreasing rates in the selected groups of outcomes. The adjustment for the healthy worker survivor effect by g-estimation in paper IV suggested that exposure from respirable dust was associated with elevated mortality risks that could not be observed with standard analytical methods.

Conclusion Our studies found several rates from the cohorts that were elevated compared to external refererence populations but also that long term employments generally were associated with decreasing rates. Furthermore, incidental lung cancer rates was found elevated for the metal refiners. Among the miners, mortality rates of cerebrovascular diseases depended on if work was performed outdoor (higher rates) or underground (lower rates). Methodologically, this thesis has discussed different analytical strategies for handling confounding in occupational cohort studies. Paper IV showed that the healthy worker survivor effect could be adjusted for by performing g-estimation.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2013. 69 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1605
Keyword
Cohort, mortality, incidence, risk, rate, cancer, cerebrovascular diseases, exposure, occupational, mining, industry, worker, Poisson regression, Cox regression, SMR, causal inference, G-estimation
National Category
Environmental Health and Occupational Health
Research subject
Occupational and Environmental Medicine; Epidemiology
Identifiers
urn:nbn:se:umu:diva-81764 (URN)978-91-7459-742-4 (ISBN)
Public defence
2013-11-15, Tripple helix, Samverkanshuset, Umeå Universitet, Umeå, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2013-10-25 Created: 2013-10-21 Last updated: 2013-10-25Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Björ, OveJonsson, HåkanDamber, LenaBurström, LageNilsson, Tohr
By organisation
Occupational and Environmental MedicineDepartment of Radiation Sciences
Environmental Health and Occupational Health

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 91 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf