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Table 3 Linear mixed effects models of DNA damage measures in roofers (samples from 20 workers at 4 sampling periods, n = 79)

From: Short-term markers of DNA damage among roofers who work with hot asphalt

  Estimate (SE) p-value
A) Model for γH2axa (lymphocytes)
Fixed effects
 Intercept 6.97 (0.04) <0.0001
 Smoker (yes/no) 0.085 (0.04) 0.04
 Period 2 (Monday, after work) 0.09 (0.03) 0.008
 Period 3 (Thursday, before work) 0.06 (0.03) 0.06
 Period 4 (Thursday, after work) 0.1 (0.03) 0.006
 Period 1 (Monday, before work) 0 (ref.)  
Random effects
 Between-subject variance 0.006 (0.002) 0.02
 Within-subject variance 0.011 (0.002) <0.0001
 Intraclass correlation coefficient % 35.3  
B) Model for 8-OHdGa (urine)
Fixed effects
 Intercept 6.99 (0.19) <0.0001
 Urine creatininea (g/L) 0.68 (0.08) <0.0001
 Period 2 (Monday, after work) 0.55 (0.12) <0.0001
 Period 3 (Thursday, before work) 0.13 (0.12) 0.27
 Period 4 (Thursday, after work) 0.50 (0.12) 0.0002
 Period 1 (Monday, before work) 0 (ref.)  
Random effects
 Between-subject variance 0.007 (0.02) 0.32
 Within-subject variance 0.14 (0.03) <0.0001
 Intraclass correlation coefficient % 4.8  
  1. a Analyses are done after (natural) logarithmic transformation