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Table 3 Chronic respiratory questions asked in a study of male coal miners comparing numbers and percentage of the affected among development, mine and other production workers stratified by smoking habit

From: High prevalence of respiratory symptoms among workers in the development section of a manually operated coal mine in a developing country: A cross sectional study

Respiratory symptoms   Development workers n(%) Mine workers n(%) Others production workers0 n(%) Total n(%) P 1
Do you usually cough first thing in the morning? Never smoker 8(20.5%) 14(25.9%) 20(21.1%) 42(22.3%) 0.754
  All 10(21.3%) 21(26.9%) 29(23.2%) 60(24.0%) 0.741
Do you usually cough during the day or at night? Never smoker 11(28.2%) 14(25.9%) 19(20.0%) 44(23.4%) 0.520
  All 13(27.7%) 21(26.9%) 28(22.4%) 63(25.2%) 0.593
If the response was yes to any of the above, the worker was asked:       
Do you usually cough as much as 4–6 times a day for 4 or more days in a week? (Yes/no) Never smoker 8(20.5%) 6(11.1%) 4(4.2%) 18(9.6%) 0.013
  All 11(23.4%) 10(12.8%) 7(5.6%) 14(5.6%) 0.004
Have you coughed like this on most of days for as much as 3 consecutive months or more in a year? (Yes/no) Never smoker 4(10.3%) 2(3.7%) 3(3.2%) 9(4.8%) 0.197
  All 5(10.6%) 5(6.4%) 4(3.2%) 14(5.6%) 0.156
For cough with sputum production, a worker was asked:       
Do you usually cough with sputum first thing in the morning? (Yes/no) Never smoker 7(17.9%) 10(18.5%) 12(12.8%) 29(15.5%) 0.580
  All 9(19.1%) 15(19.2%) 18(14.3%) 42(16.9%) 0.614
Do you usually cough with sputum during the day or at night? (Yes/no) Never smoker 7(17.9%) 8(14.8%) 8(8.4%) 23(12.2%) 0.246
  All 9(19.1%) 12(15.4%) 12(9.6%) 33(13.2%) 0.203
If the response was yes to any of the above:       
Do you usually cough with sputum as much as 4–6 times a day, or 4 or more days in a week? (Yes/no) Never smoker 4(10.5%) 3(5.6%) 2(2.1%) 9(4.8%) 0.117
  All 4(8.7%) 6(7.7%) 5(4.0%) 15(6.0%) 0.393
Have you coughed with sputum on most of days for as much as 3 consecutive months or more in a year? (Yes/no) Never smoker 3(7.7%) 1(1.9%) 0 4(2.1%) 0.019
  All 3(6.4%) 2(2.6%) 3(2.4%) 8(3.2%) 0.387
Workers were classified as having breathlessness if they answered yes to:       
Are you troubled by shortness of breath when hurrying on level ground? (Yes/no) Never smoker 17(43.6%) 17(31.5%) 33(34.7%) 67(35.6%) 0.469
  All 21(44.7%) 25(32.1%) 40(32.0%) 86(34.4%) 0.258
Do you get shortness of breath walking with other people of your own age on level ground? (Yes/no) Never smoker 7(17.9%) 2(3.7%) 3(3.2%) 12(6.4%) 0.004
  All 8(17.0%) 5(6.4%) 3(2.4%) 16(6.4%) 0.002
If the response was yes to any of the above:       
Do you have to stop for breathing when walking at your own pace on level ground? (Yes/no) Never smoker 2(5.1%) 1(1.9%) 3(3.2) 6(3.2%) 0.675
  All 3(6.4%) 4(5.1%) 4(3.2%) 11(4.4%) 0.617
Have you experienced wheezing sound from your chest? (Yes/no) Never smoker 5(12.8%) 4(7.4%) 5(5.4%) 14(7.5%) 0.335
  All 6(12.8%) 6(7.7%) 8(6.5%) 20(8.1%) 0.403
  1. 1Chi-square test between the three groups of workers
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