The percentage of patients in each group that still smoked was not significantly different (33 percent vs 32 percent, respectively; x2== 0.049, p = 0.825). There was no difference in the history of bronchitis (50 percent vs 54.1 percent, respectively; p = 0.474) or emphysema (15 percent vs 5.4 percent, respectively; p = 0.155) between the two groups. There was no difference between the groups in the family history of asthma or skin allergies (65 percent, 13 of 20, vs 63.5 percent, respectively; p = 0.554). The groups showed no significant difference (50 percent vs 52.7 percent, respectively; p=0.924) in the percentage of patients with a prior diagnosis of allergies. Although patients classified as having probable or possible occupational asthma were 6.8 years older at the time of diagnosis than those classified as not having occupational asthma (32.5 vs 25.7 years), this difference was not statistically significant. The percentage of adult patients whose asthma can be attributed to occupational exposure is not known. canadian family pharmacy online
Previous estimates have ranged from 2 to 15 percent. Our study applied NIOSH criteria to questionnaire data derived from interviews of adult patients with a primary hospital discharge diagnosis of asthma in 1990 from three Michigan hospitals in Detroit, Flint, and Lansing. We found 3 percent of the patients who were interviewed met our criteria for probable occupational asthma and 18.1 percent met our criteria for possible occupational asthma. We adjusted for a differential response rate to our questionnaire among patients from the three hospitals. The adjusted percentage of possible occupational asthmatics is 17.2 percent if we assume the nonrespondents had the same prevalence of possible occupational asthma as the respondents or 9.9 percent assuming none of the nonrespondents had possible occupational asthma. If the percentage of probable and possible occupational asthmatics (12.9 percent to 20.2 percent) were applied to all hospitals in the state, then annually 1,419 to 2,222 of the 11,000 hospital discharges due to asthma in Michigan could be attributable to work exposure. For just probable occupational asthmatics, the estimate would be 330.
The patients who met the criteria for probable or possible occupational asthma were similar to the patients not having occupational asthma. Both groups had a similar age of diagnosis, history of smoking, family history of asthma, and history of allergies. The two groups also had similar percentages of patients with a history of emphysema and bronchitis.