Clinical predictors of mortality from asbestosis in the North American Insulator Cohort, 1981 to 1991.

Recorded mortality from asbestosis has increased markedly in the United States in recent decades, from 0.49 to 3.06 per million persons between 1970 and 1990. Although asbestosis is generally considered to be a slowly progressive disorder, little is known about how clinical and exposure parameters among individuals with asbestosis quantitatively predict subsequent risk of death from asbestosis. We followed 2,609 insulators from the North American insulator cohort 10 yr to determine cause of death and to relate clinical findings to risk of death. This group had undergone clinical and radiologic examination between 1981 and 1983 in 19 cities in the United States. Seventy-four (11.0%) of 674 deaths during the subsequent 10 yr were due to asbestosis, according to the best clinical and radiologic evidence available at the time of death. The 10 yr risk of death (expressed as a percentage) due to asbestosis rose sharply with increasing interstitial fibrosis as identified on the baseline chest X-ray, from 0.9% to 2.4%, 10.8%, and 35.4% for International Labor Office (ILO) profusion categories 0, 1, 2, and 3, respectively. Dyspnea, a low FVC, and/or physical examination findings typical of interstitial fibrosis (rales, clubbing, or cyanosis) raised the risk of subsequent death from asbestosis by 2- to 6-fold. The effect of cigarette smoking on risk of death from asbestosis was small and disappeared after adjustment for ILO profusion score.