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Table 2 Distribution of confounding factors by the distance classes in males and females.

From: Geographical information system and environmental epidemiology: a cross-sectional spatial analysis of the effects of traffic-related air pollution on population respiratory health

  Males(n = 944) Females(n = 1118)
  Distance of residence to main road Distance of residence to main road
  <100 m 100-250 m 250-800 m <100 m 100-250 m 250-800 m
  n = 263M n = 279 n = 402 n = 322 n = 332 n = 464
  % % % % % %
Age (years)       
8-24 19.4 22.6 19.7 13.4* 16.9 18.1
25-64 56.7 60.9 58.7 55.5 61.4 58.0
65-97 19.9 16.5 21.6 31.1 21.7 23.9
Smoking habits       
smokers 27.3 26.9 30.6 17.7 17.5 16.6
ex-smokers 43.4 39.8 39.3 17.7 16.2 16.6
non-smokers 29.3 33.3 30.1 64.6 66.3 66.8
Passive smoking exposure       
yes 59.1 57.7 58.2 43.2 # 49.1 51.3
no 40.9 42.3 41.8 56.8 50.9 48.7
Educational level       
low 41.1 45.2 42.3 65.5 # 57.8 56.9
medium 30.4 31.9 30.1 14.6 21.4 22.6
high 28.5 22.9 27.6 19.9 20.8 20.5
Work position       
manager/white collar 13.7 17.9 19.2 8.9 * 16.7 13.7
blue collar/farmer 19.5 19.7 20.3 10.1 6.1 8.7
merchant/craftsman 17.6 15.4 12.0 9.5 6.4 8.7
unemployed 49.2 47.0 48.5 71.5 70.8 68.9
Occupational exposure       
yes 57.0 59.5 57.7 26.4 # 25.9 32.3
no 43.0 40.5 42.3 73.6 74.1 67.7
Number of hours at home       
≥ 15 h 41.1 37.6 39.3 74.2 71.1 69.8
< 15 h 58.9 62.4 60.7 25.8 28.9 30.2
Time of residence       
< 5 years 14.2 10.8 11.0 11.6 8.1 11.2
≥ 5 years 85.8 89.2 89.0 88.4 91.9 88.8
Type of self-reported environmental contamination       
traffic 92.4*** 65.2 75.2 93.6 *** 74.8 78.5
other 7.6 34.8 24.8 6.4 25.2 21.5
  1. *** p < 0.001, ** p < 0.01, * p < 0.05, # 0.05 < p < 0.1 (borderline) from Pearson chi-square test; comparison between subjects living at different distances from the main road, separately in males and in females