Friday, July 22, 2005

Vitamin A, bronchial metaplasia, and Asbestos

The Vitamin A chemoprevention study rained down money on occupational health research, in the NCI's hope of finding an alternative to reducing exposure for cancer prevention. To be fair, it would be nice to have some palliative to give to former asbestos workers or smokers.

As BrooklynDodger's readers will know, Vitamin A actually potentiated carcinogenicity of past asbestos and smoking, and the study was stopped. The study yielded valuable data in the control or placebo arm.

This paper came before the fall.

Apparently bronchial metaplasia, on biopsy, was considered a precursor to lung cancer. The paper is in the period before full text internet access, so the Dodger has read but the abstract. It would appear bronchial metaplasia was rare, in this super high risk cohort for lung cancer. The investigators buy a marginally significant result with a lower odds ratio, than a higher odds ratio which fails to achieve statistical significance.

Am J Clin Nutr. 1998 Sep;68(3):630-5.

Dietary vitamin A and prevalence of bronchial metaplasia in asbestos-exposed workers.

Mayne ST, Redlich CA, Cullen MR.Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520-8034, USA. Susan.Mayne@Yale.Edu

... Bronchial biopsies were obtained from 49 asbestos workers... Results indicated that workers with metaplasia reported consuming a significantly lower intake of total vitamin A ... than did subjects without metaplasia ... Logistic regression analyses showed that higher intakes of retinol ... provitamin A carotenoids ... and total vitamin A ... were associated with a nonsignificant reduction in the OR for metaplasia (highest quartile compared with lowest quartile, adjusted ORs). Current smoking ... and former smoking ...were associated with a nonsignificant increase in the OR for bronchial metaplasia compared with never smoking. Greater airway obstruction...was associated with an increased OR for metaplasia (OR: 2.86; 95% CI: 1.09, 7.69). These results suggest that a higher (ie, above the median) intake of vitamin A from foods decreases the risk of bronchial metaplasia in workers occupationally exposed to asbestos.

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