Plasma retinol, carotene and vitamin E concentrations and lung function in a crocidolite-exposed cohort from Wittenoom, Western Australia: a cohort study

Our plain-English summary of Plasma retinol, carotene and vitamin E concentrations and lung function in a crocidolite-exposed cohort from Wittenoom, Western Australia: a cohort study, by H.S. Alfonso, L. Fritschi, N.H. de Klerk, et al (Nutrition Journal, 2005).

The study

• Authors: H.S. Alfonso, L. Fritschi, N.H. de Klerk, G. Ambrosini, J. Beilby, N. Olsen, A.W. Musk
• Journal: Nutrition Journal
• Published: 2005;4:16
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Increased rates of death from asbestos related diseases have been reported for people previously employed in the mining and milling operations at Wittenoom (Western Australia), and people who lived in the nearby town, where they were environmentally exposed to crocidolite.

Methods: Annual measurements of forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) and plasma concentrations of retinol, carotene and vitamin E have been made since 1992. Mixed effects models were used to examine the associations between lung function and the plasma vitamin levels of retinol, carotene and vitamin E.

Results: After adjusting for potential confounders, higher plasma retinol and carotene concentrations were significantly associated with higher levels of lung function at entry into the study, while vitamin E concentrations were associated with lower entry lung function. Retinol was associated with a less steep decline of lung function over time, while carotene concentrations were associated with an increased decline of lung function over time and vitamin E levels were not associated with changes of lung function over time.

Conclusion: These results support a beneficial relationship between plasma concentrations of retinol on the levels and rates of change of lung function, while showing no such consistent beneficial effect for plasma levels of beta-carotene or vitamin E.

In plain English

This cohort study followed 1,378 crocidolite-exposed former workers and residents of Wittenoom, Western Australia, in a Vitamin A Program. The authors analysed 5,750 same-day measurements of lung function (FEV1 and FVC) and plasma retinol, carotene and vitamin E, adjusting for age, sex, height, asbestos exposure and smoking. Analysed alone, retinol was not associated with lung function at entry, but people in the highest retinol quartile lost 11.3 ml (95% CI 4.8 to 17.7) less FEV1 per year than those in the lowest. Analysed alone, higher carotene and higher vitamin E were linked to better entry lung function but steeper yearly decline. With all three vitamins in one model, retinol was linked to slower decline, carotene to higher entry values but steeper decline, and vitamin E to lower entry values with no link to decline. Retinol's link to higher entry values in this model had p-values of 0.06 and 0.08. The authors concluded the results support a beneficial relationship for retinol but not for beta-carotene or vitamin E. They noted participants were self-selected and actual vitamin intake was not measured.

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: Longitudinal cohort study with repeated measurements, analysed with mixed-effects models
• Who was studied: 1,378 former workers (811) and former residents (567) of Wittenoom, Western Australia, aged 25 or over. All took part in the Vitamin A Program and had at least one same-day spirometry and blood vitamin test between 1992 and 23 September 2002.
• Exposure: Crocidolite exposure came from mining and milling work or from living in the nearby town. It was measured as worker or resident status, age at first exposure, estimated cumulative exposure and radiographic asbestosis. The main factors studied were plasma levels of retinol, carotene (alpha- and beta-carotene) and vitamin E (alpha-tocopherol) in participants of a vitamin supplement program.
• Main results:
  • 5,750 determinations from 1,378 subjects were analysed
  • Retinol analysed as a single vitamin: plasma retinol was not associated with lung function at entry (p for linear trend 0.36 for FEV1, 0.50 for FVC)
  • Retinol analysed as a single vitamin: the annual decline in the highest retinol quartile was 11.3 ml (95% CI 4.8 to 17.7) less steep for FEV1 than in the lowest quartile. For FVC it was 18.6 ml (95% CI 10.4 to 26.8) less steep.
  • Carotene analysed as a single vitamin: higher carotene was associated with higher lung function at entry but with a steeper decline. The difference in annual FEV1 decline between the highest and lowest quartiles was given as 9.3 ml.
  • Vitamin E analysed as a single vitamin: higher vitamin E was associated with higher lung function at entry but with a steeper decline. In the highest versus lowest quartile, the extra decline was 7.9 ml per year in FEV1 and 13.9 ml per year in FVC.
  • All three vitamins in one model: retinol was associated with a slower annual decline (p = 0.02 for FEV1, p = 0.00 for FVC). Its association with entry level had p = 0.06 for FEV1 and p = 0.08 for FVC.
  • All three vitamins in one model: carotene was associated with higher entry lung function but a steeper decline over time
  • All three vitamins in one model: vitamin E was associated with lower entry lung function but not with change over time
• The authors' conclusion: The authors concluded that the results support a beneficial relationship between plasma retinol and both the level and the rate of change of lung function. They found no consistent beneficial effect for plasma beta-carotene or vitamin E.
• Limitations the authors state:
  • Participants self-selected into the Vitamin A Program and may not represent the whole Wittenoom cohort. Results may not apply to people with lower crocidolite exposure or older age groups.
  • Vitamin levels were raised by supplements, and there was no precise measure of actual vitamin intake or of dietary fruit and vegetable intake
  • Ninety participants (6.3%) dropped out, and they had lower lung function than those who remained. The analysis assumed data were missing at random.
  • Smoking was self-reported and measured only at entry, so changes in smoking over time were not analysed

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Wittenoom, Western Australia

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Crocidolite, Wittenoom, Cohort Study, FEV1.

Related studies

• Plasma vitamin concentrations and incidence of mesothelioma and lung cancer in individuals exposed to crocidolite at Wittenoom, Western Australia — H.S. Alfonso, L. Fritschi, et al. (2006)
• Retinol supplementation and mesothelioma incidence in workers earlier exposed to blue asbestos (Crocidolite) at Wittenoom, Western Australia — H.S. Alfonso, A. Reid, et al. (2010)
• Effects of asbestos and smoking on the levels and rates of change of lung function in a crocidolite exposed cohort in Western Australia — H.S. Alfonso, L. Fritschi, et al. (2004)
• Vitamin A and cancer prevention I: observations in workers previously exposed to asbestos at Wittenoom, Western Australia — A.W. Musk, N.H. de Klerk, et al. (1998)
• Vitamin A and cancer prevention II: comparison of the effects of retinol and beta-carotene — N.H. de Klerk, A.W. Musk, et al. (1998)
• Changes in cholesterol and triglyceride concentrations in the Vanguard population of the Carotene and Retinol Efficacy Trial (CARET) — B. Cartmel, J. Dziura, et al. (2005)

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