Symptom Persistence: When symptom consistency was examined in relation to pulmonary function, workers who consistently reported the presence of symptoms exhibited an accelerated decline in ventilatory capacity compared with those who never or inconsistently reported these symptoms (Table 3). As a group, those subjects with typical byssinosis, any chest tightness at work and chronic bronchitis, also tended to have more work years, higher dust exposure, and a higher prevalence of smoking. In addition, a high rate of loss (—139 ml/yr) was noted among the four subjects with byssinosis who reported typical byssinosis on both surveys (data not shown).
Symptoms at Initial Survey: When subjects with incident and resolved symptoms were examined separately, there were no statistically significant differences in age or work characteristics. There were significant differences in subjects who report symptoms of chronic cough and dyspnea at the time of the first survey in relation to the 5-year change in pulmonary function (Fig 2). Overall, subjects who reported any of the four respiratory symptoms at the time of the first survey suffered an accelerated loss of lung function over the subsequent 5 years (—234 ml vs —186 ml, p=0.07). Canadian family pharmacy there The symptoms which were associated with the most significant declines in FEVi were chronic cough and dyspnea. When examined in an autoregressive model, after adjustments for baseline FEVi, age, height, gender, and smoking history, the presence of chest tightness at work, chronic cough, or dyspnea 2+ at the time of initial survey was associated with a significant 5-year loss in FEVi (Table 4).
Acute and chronic changes in ventilatory capacity were examined in the cohort of workers tested at both surveys. The groups across-shift change in FEVi was comparable between the two surveys and the mean preshift ventilatory function was 98 percent of predicted at the time of the second survey (Table 2).
No statistically significant differences were detected either in 1981 or 1986 in preshift levels of FEVi among subjects stratified by consistency of across-shift change, although there was a trend toward larger loss for workers who were consistently pulmonary function responders (Table 5).
Table 2—Comparison of Symptom Prevalence and Pulmonary Function at Initial Survey in Subjects Seen at Follow-Up and Subjects Unavailable for Follow-Up
|Clinical Data||Follow-Up||Unavailable for Follow-Up|
|Years worked (mean)||15.8||19.1|
|Chest tightness at work||7.5||9.7|
|Byssinosis (all grades)||7.3||9.7|
|Pulmonary Function ||
|FEVi percent predicted (1981 )§||99.8 ±13.4||98.1 ±15.0|
|% Д FEV! (1981)||||—1.90±5.6||-2.78 ±5.8|
|FEV! % predicted (1986)||97.6 ±14.8|
|% Д FEV, (1986)||—1.76±6.6|
|FEVi 5-yr ДЦ||-0.203 ±0.21|
Table 3—Characteristics by Symptom Consistency
|Chest Tightness||Chronic Bronchitis||Chronic Cough||Dyspnea 2+||Union t|
|Sex (% male)||51||41||50||43||61||79||44||55||78||52||42||45||50||44||53|
|Work years (1981)||15||17||19||15||17||20||15||16||21||15||17||20||15||16||18|
|FEVi % predicted 1981||100||101||91||100||101||94||101||99||95||101||99||93||101||100||97|
|FEVi % predicted 1986||98||98||87||98||100||87||99||97||89||100||96||85||99||99||93|
Table 4—Regression Coefficients for Initial FEVj, Age, Height, Smoking, and symptoms in Pulmonary Function Models
|Consistency of AFEVi<—5%|
|First survey % predicted FEVi*||99.3 ±12.5||99.6 ±12.9||98.2 ±14.7|
|Second survey % predicted FEVi||98.3 ±14.4||96.6 ±14.0||94.4 ±19.3|
|FEVi 5-year A (ml)t||—180±197||-224 ±249||—267 ± 192
Table 5—Cross-Sectional Mean Levels of Pulmonary Function According to Consistency of Across-Shift Drop in FEVj
|Outcome variable=FEVi 1986 (L)|
|Independent variable||Parameter Estimate||p>N||r2|
|Current smoking (0,1)||-0.017||0.47|
|Current smoking (0,1)||-0.020||0.035|
|Current smoking (0,1)||-0.022||0.35|
Figure 2. Subsequent 5-year loss of lung function in subjects with various respiratory symptoms at initial survey. CTW, chest tightness at work; CB, chronic bronchitis; CC, chronic cough; DYS, dyspnea; UNION, union of symptoms.