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Table 1 Demographic characteristics of study subjects

From: A missense variant rs2585405 in clock gene PER1 is associated with the increased risk of noise-induced hearing loss in a Chinese occupational population

Variables Cases (n = 432) Controls (n = 837) P
n % n %  
Age (years) 0.09a
Mean ± SD 47.85 ± 5.48 47.43 ± 5.38 0.18b
 ≤ 35 13 1.0 26 2.1  
35–45 89 7.0 219 17.3  
 > 45 330 26.0 592 46.7  
Sex 0.40a
Male 392 30.9 771 60.8  
Female 40 3.2 66 5.2  
Tobacco use 0.93a
Now 194 15.3 372 29.3  
Ever 170 13.4 338 26.6  
Never 68 5.4 127 10.0  
Alcohol consumption 0.79a
Now 192 15.1 356 28.1  
Ever 33 2.6 63 5.0  
Never 207 16.3 418 32.9  
Duration of noise exposed work (years) 0.75a
Mean ± SD 23.72 ± 10.58 23.68 ± 10.55 0.95b
 ≤ 16 84 6.6 169 13.3  
 > 16 348 27.4 668 52.6  
Noise exposure levels (dB) 0.17a
 ≤ 85 265 20.9 474 37.4  
85–92 126 9.9 288 22.7  
 > 92 41 3.2 75 5.9  
High frequency hearing thresholds (dB)  < 0.001 a
Mean ± SD 0.64 ± 0.48   0  < 0.001 b
 ≤ 26 155 12.2 837 66.0  
 > 26 277 21.4 0 0.0  
  1. aStudents’ t-test
  2. bTwo-sided χ2 test