Occupational risk factors for chronic respiratory disease in a New Zealand population using lifetime occupational history

Our plain-English summary of Occupational risk factors for chronic respiratory disease in a New Zealand population using lifetime occupational history, by A. Hansell, R.E. Ghosh, S. Poole, et al (Journal of Occupational and Environmental Medicine, 2014).

The study

• Authors: A. Hansell, R.E. Ghosh, S. Poole, J.P. Zock, M. Weatherall, R. Vermeulen, H. Kromhout, J. Travers, R. Beasley
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2014;56(3):270-80
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To investigate associations between respiratory disease and occupational exposures in a New Zealand urban population, the Wellington Respiratory Survey.

Methods: Multiple regression analyses in a population sample of 1017 individuals aged 25 to 74 years with spirometry and questionnaire information, including a lifetime occupational history.

Results: Chronic bronchitis symptoms were associated with self-reported exposure to hairdressing, paint manufacturing, insecticides, welding, detergents and with ALOHA Job Exposure Matrix-assessed gases/fumes exposure. The strongest association was for hairdressing (odds ratio 6.91; 95% confidence interval: 2.02 to 23.70). Cumulative exposure to mineral dust and gases/fumes was associated with higher FEV₁% (forced expiratory volume in the first second of expiration) predicted. Analyses were limited by relatively small numbers of cases.

Conclusions: Increased risks of objectively defined respiratory disease, which have been previously documented, were not seen. Nevertheless, the study suggested increased risk of respiratory symptoms with various occupational exposures as well as likely healthy worker effect.

In plain English

This cross-sectional study used the Wellington Respiratory Survey, carried out in 2003 to 2004 in Wellington, New Zealand. Of 1017 adults aged 25 to 74 who completed a detailed questionnaire with a lifetime job history, 750 also had valid lung function tests. Workplace exposure was measured in two ways: self-report of 18 exposures, including asbestos (reported by 109 people), and a job exposure matrix for dusts, gases and fumes. Chronic bronchitis symptoms were associated with self-reported hairdressing (odds ratio 6.91; 95% CI 2.02 to 23.70). This was the only self-reported link that stayed significant after correcting for multiple testing. Detergents, paint manufacturing, insecticides and welding showed weaker links. Self-reported asbestos exposure showed no statistically significant association with COPD on lung testing, doctor-diagnosed COPD or chronic bronchitis symptoms. It was linked to higher lung function, but not significantly after multiple-testing correction. Some exposures were linked to better lung function, which the authors put down to a likely healthy worker effect. The authors concluded that increased risks of objectively defined respiratory disease were not seen. They noted small numbers as a limitation.

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: Cross-sectional population survey analysis (logistic and linear regression)
• Who was studied: 1017 adults aged 25 to 74 from an age-stratified random sample of the electoral roll in Wellington, New Zealand, surveyed in 2003 to 2004. 750 of them also had valid postbronchodilator lung function data.
• Exposure: Two measures of exposure: self-reported exposure to 18 occupational exposures or work circumstances, including asbestos (reported by 109 people, 10.7%), and the ALOHA job exposure matrix applied to lifetime job histories for biological dust, mineral dust, gases/fumes and any vapors, gases, dusts or fumes (VGDF).
• Main results:
  • Chronic bronchitis symptoms in those reporting hairdressing exposure: OR 6.91 (95% CI 2.02 to 23.70; q = 0.034). This was the only self-reported exposure that remained significant after multiple-testing correction.
  • Chronic bronchitis symptoms were also raised with self-reported detergents (OR 2.16; 95% CI 1.13 to 4.09), paint manufacturing (OR 3.46; 95% CI 1.09 to 11.05), insecticides (OR 2.35; 95% CI 1.05 to 5.26) and welding (OR 2.27; 95% CI 1.02 to 5.08). Each had q = 0.153, which was not significant after multiple-testing correction.
  • Self-reported asbestos exposure and chronic bronchitis symptoms: 10 of 109 exposed people had symptoms; adjusted OR 0.98 (95% CI 0.38 to 2.52). This was not statistically significant.
  • Self-reported asbestos exposure and COPD defined by spirometry below the lower limit of normal: 16 of 91 exposed people; adjusted OR 1.04 (95% CI 0.43 to 2.48). This was not statistically significant.
  • Self-reported asbestos exposure and doctor-diagnosed COPD: 12 of 109 exposed people; adjusted OR 0.94 (95% CI 0.41 to 2.12). This was not statistically significant.
  • Self-reported exposure to solvents, detergents and asbestos was associated with about 3% to 5% higher FEV1% predicted. For asbestos the adjusted figure was 5.39 (95% CI 0.54 to 10.25). None of these associations had significant q-values.
  • Using the job exposure matrix, chronic bronchitis symptoms were raised with only ever low mineral dust exposure (OR 2.04; 95% CI 1.06 to 3.93) and ever high gas or fumes exposure (OR 2.10; 95% CI 1.11 to 3.98). Both reached conventional but not multiple-testing-adjusted significance.
  • Ever high gases or fumes exposure was associated with a 5.83% higher FEV1% predicted (95% CI 1.94 to 9.71; q = 0.024), which remained significant after multiple-testing correction.
  • Cumulative exposure showed no associations with COPD on spirometry, doctor-diagnosed COPD or chronic bronchitis symptoms.
• The authors' conclusion: The authors concluded that increased risks of objectively defined respiratory disease were not seen. They found that people were more likely to report chronic bronchitis symptoms with several occupational exposures. They interpreted the higher lung function in some exposed groups as evidence suggestive of a healthy worker effect.
• Limitations the authors state:
  • Relatively small numbers in some occupational groups reduced the power to detect associations.
  • There were fewer people in older age groups, and COPD usually appears in late middle or old age.
  • Possible bias from selection and reporting, the healthy worker effect and job selection, plus possible error from multiple comparisons.
  • Some observed associations may relate to asthma rather than COPD, given the high asthma prevalence in this population.
  • Wellington had relatively few people in heavy industry, farming and mining, and the sample was less deprived than New Zealand as a whole. Highly exposed people may therefore have been underrepresented.
  • Adjusting for age may have over-adjusted for exposure.

Topics

Medical terms in this study, explained in our Lexicon: Occupational History, Occupational Exposure, Spirometry, Odds Ratio, confidence interval, Cumulative Exposure, Healthy Worker Effect.

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