The GW 572016 fit of the generalised linear mixed model was assessed using the variance of the Pearson residual. Test for trend was performed using linear scores for tertiles. The analyses were performed using SAS 9.1 (PROC GENMOD and PROC GLIMMIX) (SAS Institute Inc. 2004. SAS OnlineDoc® 9.1.3. Cary, NC: SAS Institute Inc.). Results The distribution of symptoms by symptom score is shown in Table 3.

Apart from symptoms of chronic bronchitis, the prevalence of each of the symptoms was approximately independent of symptom score (10–20%). There were 584 dropouts during the study. Table 3 The prevalence (% in parentheses) of each symptom by symptom score Symptom score Dyspnéa Wheezing Cough without cold Cough >3 months last year Phlegm when coughing 0 0 0 0 0 0 1 91 (13.7) 47 (8.3) 151 (20.2) 1 (0.4) 120 (19.2) 2

167 (25.2) 136 (24.0) 177 (23.7) 30 (11.7) 130 (20.8) 3 153 (23.1) 145 (25.6) 162 (21.7) 54 (21.1) 140 (22.4) 4 149 (22.5) 136 (24.0) 155 (20.7) 69 (26.9) 131 (21.0) 5 103 (15.5) 103 (18.2) 103 (13.8) 103 (40.1) 103 (16.5) Total 663 (100.0) 567 (100.0) 748 (100.0) 257 (100.0) 624 (100.0) The mean and PF-3084014 nmr the variance of symptom score during the follow-up by relevant Vorinostat mw covariates are shown in Table 4. Generally, the magnitude of the variance was twice the mean, indicating some overdispersion in the data. Except from dropouts, symptom score appeared to decline during the follow-up. However, a dose–response relationship between symptom score and smoking was indicated at each follow-up. Moreover, line operators had generally higher symptom score than non-line operators, who had higher symptom score than non-exposed Phloretin employees. The standard deviation of symptom score between and within individuals was 1.2 and 0.75, respectively. Table 4 Mean symptom score and the corresponding variance (in parentheses) during follow-up by relevant covariates Covariate Follow-up no. Baseline 1 2 3 4 5 Gender  Male 1.02 (2.13) 0.97 (2.12) 0.92 (2.01) 0.89 (2.02) 0.83 (1.94) 0.78 (1.86)  Female 0.71 (1.38) 0.66 (1.55) 0.62 (1.51) 0.57 (1.28) 0.52 (1.30) 0.61 (1.71) Age (years)  20–34 0.87 (1.75) 0.84 (1.87) 0.75 (1.66) 0.70 (1.51) 0.65 (1.38) 0.45 (1.20)  35–44 1.05 (2.21) 1.00

(2.22) 0.93 (2.06) 0.92 (2.23) 0.74 (1.77) 0.77 (1.86)  45+ 1.05 (2.23) 0.96 (2.09) 0.94 (2.06) 0.87 (1.92) 0.89 (2.11) 0.84 (1.97) Smoking  Never smoker 0.60 (1.31) 0.49 (1.08) 0.49 (1.10) 0.46 (1.20) 0.48 (1.24) 0.48 (1.25)  Former smoker 0.73 (1.58) 0.66 (1.49) 0.59 (1.39) 0.56 (1.36) 0.56 (1.27) 0.60 (1.51)  Current (cig/day)  1–9 1.04 (2.18) 1.05 (2.27) 0.99 (2.10) 0.98 (2.02) 0.92 (2.03) 0.78 (1.68)  10–19 1.49 (2.48) 1.46 (2.74) 1.45 (2.61) 1.44 (2.63) 1.32 (2.71) 1.31 (2.75)  20+ 2.22 (3.36) 2.31 (2.57) 1.81 (3.08) 1.65 (2.70) 1.72 (2.94) 1.55 (2.76) Job categories  Unexposed 0.62 (1.26) 0.65 (1.53) 0.65 (1.50) 0.62 (1.52) 0.61 (1.51) 0.87 (2.11)  Non-line operators 0.96 (2.04) 0.93 (2.17) 0.85 (1.90) 0.81 (1.90) 0.80 (2.06) 0.77 (1.