Navy Asbestos Medical Surveillance Program 1990-1999: demographic features and trends in abnormal radiographic findings

Our plain-English summary of Navy Asbestos Medical Surveillance Program 1990-1999: demographic features and trends in abnormal radiographic findings, by D.M. Dell, B.K. Bohnker, J.G. Muller, et al (Military Medicine, 2006).

The study

• Authors: D.M. Dell, B.K. Bohnker, J.G. Muller, A.F. Philippi, F.K. Litow, W.G. Rudolph, J.E. Hernandez, D.A. Hiland
• Journal: Military Medicine
• Published: 2006;171(8):717-22
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A 10-year cross-sectional analysis was conducted for 233,353 radiographic examinations performed as part of the Navy Asbestos Medical Surveillance Program. Demographic and temporal trends in abnormal radiographs were assessed during this analysis. Abnormal radiograph prevalence increased significantly with age, and abnormal radiographs were nearly 30 times more likely to occur among participants 60 to 69 years of age, compared with participants < 20 years of age (odds ratio, 27.57; 95% confidence interval, 14.75-51.53). Men were 5 times more likely than women to have an abnormal radiograph (odds ratio, 5.84; 95% confidence interval, 5.02-6.80); after controlling for differences in age, this gender association remained significant only for participants > 30 years of age. The proportion of abnormal radiographs decreased significantly over the study period [chi2 (df = 1) test for trend, chi2 = 198.7, p < 0.0001], although the cohort mean age increased. Despite aging of the Asbestos Medical Surveillance Program population, the overall prevalence of radiographic abnormalities is declining; future studies should examine the reasons for this observation.

In plain English

This cross-sectional analysis reviewed 233,353 chest X-ray records from the U.S. Navy Asbestos Medical Surveillance Program for 1990 to 1999. The program covers civilian and active duty personnel exposed to asbestos at work. The X-ray database held no information on asbestos exposure or smoking. Overall, 13.9% of X-rays were coded as showing abnormalities consistent with pneumoconiosis. That share fell from 15.5% in 1990 to 9.7% in 1999, even though the average age of those X-rayed rose from 45.2 to 48.3 years. Parenchymal (lung tissue) and pleural abnormalities also declined. Abnormal X-rays became more common with age: people aged 60 to 69 had an odds ratio of 27.57 (95% CI 14.75 to 51.53) compared with those under 20. Men had higher odds than women (OR 5.84; 95% CI 5.02 to 6.80). After the data were split by age, the difference between men and women was significant only from age 30 up. The authors concluded that the decline suggests asbestos-abatement efforts were effective, although other explanations cannot be ruled out.

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 analysis of surveillance chest X-ray records
• Who was studied: 233,353 chest X-ray records (records, not individual people) from the U.S. Navy Asbestos Medical Surveillance Program, 1990 to 1999. The program covers civilian and active duty military personnel exposed to asbestos at work. 97.3% of records were for men, and the mean age at X-ray was 46.2 years.
• Exposure: Occupational asbestos exposure: workers exposed for 30 days per year at or above the permissible exposure limit of 0.1 fibers per cm3 of air, plus workers doing class I, II or III work. No fiber types are named. Exposure information was not in the X-ray database and was not analyzed.
• Main results:
  • Across the whole study period, 13.9% of X-rays were coded as positive for pneumoconiosis.
  • The proportion of X-rays coded positive for pneumoconiosis fell from 15.5% in 1990 to 9.7% in 1999. The test for trend gave chi-square 198.7, p less than 0.0001. Significant declines were seen in both men and women.
  • The mean age of participants at the time of X-ray rose significantly over the study period, from 45.2 years in 1990 to 48.3 years in 1999.
  • Compared with participants under 20, those aged 60 to 69 had an odds ratio of 27.57 (95% CI 14.75 to 51.53) for an abnormal X-ray. 28.6% of X-rays in the 60 to 69 group were abnormal, against 1.4% in the under-20 group.
  • X-rays of men were more likely to be abnormal than X-rays of women: 14.2% versus 2.8%, odds ratio 5.84 (95% CI 5.02 to 6.80).
  • When the data were stratified by age, the association between gender and abnormal X-rays was significant only in the age groups from 30 upward (adjusted ORs 4.73 to 6.01). It was not significant in the under-20 and 20 to 29 groups.
  • X-rays were more likely to be abnormal if taken at periodic visits (OR 2.95; 95% CI 2.77 to 3.14) or termination visits (OR 2.89; 95% CI 2.68 to 3.13), compared with initial visits.
  • Parenchymal abnormalities were found on 3.6% of X-rays overall and declined over time, from 4.7% in 1990 to 2.3% in 1999.
  • Pleural abnormalities declined from 2.4% of X-rays in 1990 to 1.4% in 1999. The test for trend gave chi-square 116.1, p less than 0.0001.
• The authors' conclusion: The authors concluded that the significant decrease in abnormal readings suggests that asbestos-abatement efforts were effective, although other explanations cannot be ruled out. They also said it may be worthwhile to target future surveillance at the workers most heavily exposed to asbestos.
• Limitations the authors state:
  • Because the analysis was cross-sectional, the authors could not tell whether the decline reflected changes in individuals' X-rays or turnover in who was in the program.
  • Individual risk factors and differences between B-readers (the certified X-ray readers) could not be assessed.
  • Asbestos exposure levels and smoking history were not included.
  • There were relatively few 1999 records because data entry was halted over Y2K concerns.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, The Navy.

Medical terms in this study, explained in our Lexicon: Odds Ratio, confidence interval.

Related studies

• Trends in pleural radiographic findings in the Navy Asbestos Medical Surveillance Program (1990-1999) — J.G. Muller, B.K. Bohnker, et al. (2005)
• Variability in interpretation among B-readers in the U.S. Navy Asbestos Medical Surveillance Program — J.G. Muller, J.M. Lieske, et al. (2008)
• Changes in B-readings over time in the United States Navy Asbestos Medical Surveillance Program — J.G. Muller, W.G. Rudolph, et al. (2007)
• Navy Asbestos Medical Surveillance Program (1984-1990): linear regression analysis for effect of asbestos exposure on pulmonary function testing — B.K. Bohnker, L.S. Betts, et al. (2004)
• Navy Asbestos Medical Surveillance Program (1991-1999): linear regression analysis for the effect of asbestos exposure on pulmonary function testing — B.K. Bohnker, L.S. Betts, et al. (2004)
• 'B-readers' and asbestos medical surveillance — A.M. Ducatman, W.N. Yang, et al. (1988)

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