Frequency at each mill | |||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mill code (n) | 1 (39) | 2 (18) | 3 (36) | 4 (33) | 5 (13) | 6 (21) | 7 (11) | 8 (11) | 9 (11) | 10 (24) | 11 (8) | 12 (51) | 13 (11) | 14 (12) | 15 (73) | Overall frequency | Overall percentage (95% CI) |
Symptoms | |||||||||||||||||
Frequent cough | 8 | 2 | 3 | 7 | 2 | 4 | 1 | 1 | 4 | 4 | 0 | 9 | 1 | 1 | 15 | 62 | 16.7 (12.8 to 20.4) |
Chronic cough† | 3 | 1 | 1 | 7 | 1 | 2 | 0 | 1 | 0 | 1 | 0 | 5 | 0 | 0 | 6 | 28 | 7.5 (4.9 to 10.2) |
Frequent phlegm* | 14 | 7 | 7 | 13 | 3 | 6 | 3 | 1 | 3 | 6 | 1 | 13 | 1 | 1 | 20 | 99 | 26.6 (22.1 to 31.1) |
Chronic phlegm† | 2 | 3 | 2 | 10 | 2 | 5 | 1 | 0 | 2 | 1 | 0 | 7 | 1 | 1 | 11 | 48 | 12.9 (9.5 to 16.31) |
Frequent wheeze‡ | 13 | 6 | 9 | 11 | 2 | 10 | 5 | 6 | 5 | 3 | 0 | 27 | 7 | 3 | 41 | 148 | 39.8 (34.8 to 44.7) |
Chronic wheeze† | 3 | 4 | 4 | 8 | 2 | 3 | 2 | 3 | 5 | 1 | 0 | 17 | 4 | 2 | 25 | 83 | 22.3 (18 to 26.5) |
Shortness of breath grade 1§ | 19 | 10 | 15 | 19 | 4 | 9 | 7 | 4 | 6 | 1 | 7 | 25 | 6 | 6 | 36 | 174 | 46.8 (41.7 to 51.8) |
Shortness of breath grade 2¶ | 9 | 7 | 6 | 6 | 2 | 4 | 4 | 0 | 1 | 1 | 2 | 15 | 2 | 1 | 18 | 78 | 21 (16.8 to 25.1) |
Chest tightness ever** | 11 | 5 | 9 | 10 | 5 | 6 | 3 | 1 | 5 | 2 | 0 | 21 | 4 | 4 | 38 | 124 | 33.3 (28.5 to 38.1) |
Chest tightness apart from during cold†† | 7 | 1 | 2 | 5 | 4 | 4 | 2 | 0 | 5 | 1 | 0 | 9 | 3 | 2 | 25 | 70 | 18.8 (14.8 to 22.8) |
Illnesses | |||||||||||||||||
Byssinosis‡‡ | 4 | 1 | 0 | 2 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 5 | 1 | 2 | 23 | 39 | 10.5 (7.3 to 13.5) |
Asthma§§ | 4 | 0 | 1 | 1 | 0 | 2 | 0 | 0 | 0 | 0 | 0 | 4 | 0 | 0 | 3 | 15 | 4 (2 to 6) |
Lung function¶¶ | |||||||||||||||||
FEV1 | 94 | 96 | 94 | 93 | 84 | 91 | 96 | 103 | 104 | 93 | 87 | 83 | 101 | 98 | 102 | 94 (17.9)*** | 3.6 (<0.001)††† |
FVC | 100 | 100 | 98 | 99 | 90 | 99 | 101 | 104 | 106 | 99 | 90 | 92 | 102 | 104 | 111 | 100 (17.5) *** | 3.7 (<0.001) ††† |
FEV1/FVC¶¶ | 97 | 99 | 100 | 99 | 95 | 97 | 99 | 104 | 101 | 97 | 99 | 94 | 104 | 98 | 95 | 97 (10.4) *** | 1.7 (0.049)††† |
*Question asked: do you usually cough/bring up phlegm 5 or more days of the week?
†Chronic applies for symptoms present for more than 2 years.
‡Question asked: does your chest ever sound wheezy or whistling?
§Question asked: are you troubled by shortness of breath when hurrying on level ground, or walking up a slight hill?
¶Question asked: do you have to walk slower than people of your age, on level ground, because of breathlessness?
**Question asked: does your chest ever feel tight and/or your breathing becomes difficult?
††Question asked: does your chest feel tight and/or your breathing becomes difficult occasionally apart from cold?
‡‡Based on Schilling's criteria.
§§Question asked: has a doctor ever told you that you have asthma?
¶¶Lung function: mean percentage-predicted lung volumes at each mill.
***Overall lung volumes at all 15 mills (±SD).
†††ANOVA results: F (p value).
FEV1, Forced Expiratory Volume in the first second; FVC, Forced Vital Capacity.