Clinical Studies In Asbestosis

Our plain-English summary of Clinical Studies In Asbestosis, by M.J. Stone (1940).

The study

• Author: M.J. Stone
• Published: American Review Of Tuberculosis 41:12-21, January (1940)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 002871. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1940 article reported on 180 patients examined in 1936 and 1937 after disability claims. All had worked three years or more in a factory making asbestos brake lining for automobiles. The author found no signs of asbestosis in 32 patients. The other 148 were classified as stage I (78), stage II (54) or stage III (16). The author saw only slight evidence that fibrosis increased with length of exposure. Of 180 chest films, 9 showed tuberculous infection, 2 of them active. Of 150 patients studied for heart effects, 50 (33 per cent) had a widened heart shadow on X-ray after other heart disease was excluded. Thirteen cases, called 8 per cent of the total series, had right-sided heart hypertrophy. Thirteen patients were re-examined two to three years later. Fibrosis had clearly progressed in the two originally in stage III. Eighteen patients had died. The author concluded that tuberculosis was not a frequent companion of asbestosis. From the small follow-up group, the author's impression was that advanced fibrosis kept progressing after exposure ended but earlier stages did not. The author noted that, because all patients sought compensation, many complaints were undoubtedly exaggerated.

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: Clinical case series of patients examined after making disability claims, with a small follow-up re-examination
• Who was studied: 180 patients who had worked three years or more in a factory manufacturing asbestos brake lining for automobiles. They came to attention through disability claims and were examined in 1936 and 1937. None had worked in asbestos factories since their examinations.
• Exposure: Work in the carding, spinning or weaving rooms of an asbestos brake lining factory; many crushed crude asbestos. Most were employed five to fifteen years and many more than twenty-five years. The article does not state the fiber type these workers were exposed to.
• Main results:
  • Of 180 patients, 32 were judged negative. The remaining 148 were classified as stage I, 78 patients.
  • Of the 148 classified patients, 54 were in stage II.
  • Of the 148 classified patients, 16 were in stage III.
  • Of the 47 patients exposed four years or less, 25 showed no definite pathological changes, 14 were stage I and 8 were stage II.
  • Of the 40 patients exposed ten to fifteen years, 14 were stage I, 20 were stage II and 6 were stage III.
  • Average length of exposure was eight years for stage I patients, ten years for stage II and eleven years for stage III.
  • The author found only slight evidence that the degree of fibrosis increased with length of exposure, and cited other factors such as intercurrent infections.
  • Of 180 X-ray films, 9 showed tuberculous infection of the lung tissue.
  • Of those 9 patients with tuberculous infection, two had active tuberculosis.
  • Among the 16 cases of advanced asbestosis, only one had active tuberculosis.
  • Of 150 patients studied for heart involvement, 90 (60 per cent) showed prominent pulmonary vessels.
  • The transverse diameter of the heart was increased in 50 cases (33 per cent) after excluding cases of organic heart disease.
  • Thirteen cases, described as 8 per cent of the author's 'total series', had right-sided hypertrophy. The article does not make clear whether 'total series' means the 150 heart patients or all 180 patients.
  • Among 56 stage II and stage III cases, 35 (62 per cent) showed prominence of the pulmonary vessels. In 18 patients (32 per cent) the enlarged transverse diameter was associated with asbestosis.
  • The author believed the early dyspnoea in this disease was of cardiac or circulatory origin rather than pulmonary origin.
  • Thirteen patients were re-examined two to three years after their first examination: 2 originally stage III, 8 stage II and 3 stage I.
  • In all 13 re-examined patients, vital capacity was 50 to 75 per cent below normal.
  • X-ray showed definite progression of fibrosis in the two re-examined patients originally classified as stage III.
  • From this small follow-up group, the author's impression was that advanced fibrosis from asbestosis progresses even after exposure ceases, but not in the earlier stages.
  • Eighteen patients had died since the group was first examined. Listed causes included pulmonary tuberculosis, bronchopneumonia, lobar pneumonia, carcinoma, cardiac disease, cerebral shock, accidents and brain tumor.
  • Seventeen patients were semi-invalids, most complaining of cough and marked dyspnoea.
• The authors' conclusion: The author concluded that tuberculosis is not a frequent concomitant of asbestosis. Other listed conclusions included that advanced asbestosis not infrequently leads to right ventricular hypertrophy and failure, and that fibrosis does not progress after exposure ceases unless already marked.
• Limitations the authors state:
  • All patients were seeking compensation, and the author considered many of their complaints undoubtedly exaggerated.
  • Classifying stage I was often somewhat arbitrary, because it is hard to tell normal from exaggerated lung markings.
  • Early asbestosis could not be diagnosed with any degree of certainty.
  • The follow-up conclusions rested on a small group of 13 patients.

Topics

Medical terms in this study, explained in our Lexicon: Brake Lining, Fibrosis, Chest X-Ray.

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